In order to use HTML help in your application, you need to add the following code into a module:

' Visual Basic code for implementing HTML Help 1.1

'*****
' Declare the following two constants
' as PUBLIC
Public Const HH_HELP_CONTEXT = &HF            ' display mapped numeric
Public Const HH_TP_HELP_WM_HELP = &H11       ' text popup help, same as
                                             ' WinHelp HELP_WM_HELP

Private Const HH_DISPLAY_TOPIC = &H0
Private Const HH_HELP_FINDER = &H0            ' WinHelp equivalent
Private Const HH_DISPLAY_TOC = &H1            ' WinHelp equivalent
Private Const HH_DISPLAY_INDEX = &H2         ' WinHelp equivalent
Private Const HH_DISPLAY_SEARCH = &H3        ' not currently implemented
Private Const HH_SET_WIN_TYPE = &H4
Private Const HH_GET_WIN_TYPE = &H5
Private Const HH_GET_WIN_HANDLE = &H6
Private Const HH_ENUM_INFO_TYPE = &H7        ' Get Info type name, call
                                             ' repeatedly to enumerate,
                                             ' -1 at end
Private Const HH_SET_INFO_TYPE = &H8         ' Add Info type to filter.
Private Const HH_SYNC = &H9
Private Const HH_ADD_NAV_UI = &HA             ' not currently implemented
Private Const HH_ADD_BUTTON = &HB             ' not currently implemented
Private Const HH_GETBROWSER_APP = &HC        ' not currently implemented
Private Const HH_KEYWORD_LOOKUP = &HD
Private Const HH_DISPLAY_TEXT_POPUP = &HE    ' display string resource id
                                             ' or text in a popup window
                                             ' value in dwData
Private Const HH_TP_HELP_CONTEXTMENU = &H10  ' text popup help, same as
                                             ' WinHelp HELP_CONTEXTMENU
Private Const HH_CLOSE_ALL = &H12             ' close all windows opened
                                             ' directly or indirectly by
                                             ' the caller
Private Const HH_ALINK_LOOKUP = &H13         ' ALink version of
                                             ' HH_KEYWORD_LOOKUP
Private Const HH_GET_LAST_ERROR = &H14       ' not currently implemented
Private Const HH_ENUM_CATEGORY = &H15        ' Get category name, call
                                             ' repeatedly to enumerate,
                                             ' -1 at end
Private Const HH_ENUM_CATEGORY_IT = &H16     ' Get category info type
                                             ' members, call repeatedly to
                                             ' enumerate, -1 at end
Private Const HH_RESET_IT_FILTER = &H17      ' Clear the info type filter
                                             ' of all info types.
Private Const HH_SET_INCLUSIVE_FILTER = &H18 ' set inclusive filtering
                                             ' method for untyped topics
                                             ' to be included in display
Private Const HH_SET_EXCLUSIVE_FILTER = &H19  ' set method for untyped
                                             ' topics to be excluded from
                                             ' the display
Private Const HH_SET_GUID = &H1A              ' For Microsoft Installer --
                                             ' dwData is a pointer to the
                                             ' GUID string
Private Const HH_INTERNAL = &HFF              ' Used internally.

' Button IDs

Private Const IDTB_EXPAND = 200
Private Const IDTB_CONTRACT = 201
Private Const IDTB_STOP = 202
Private Const IDTB_REFRESH = 203
Private Const IDTB_BACK = 204
Private Const IDTB_HOME = 205
Private Const IDTB_SYNC = 206
Private Const IDTB_PRINT = 207
Private Const IDTB_OPTIONS = 208
Private Const IDTB_FORWARD = 209
Private Const IDTB_NOTES = 210                ' not implemented
Private Const IDTB_BROWSE_FWD = 211
Private Const IDTB_BROWSE_BACK = 212
Private Const IDTB_CONTENTS = 213             ' not implemented
Private Const IDTB_INDEX = 214                ' not implemented
Private Const IDTB_SEARCH = 215               ' not implemented
Private Const IDTB_HISTORY = 216              ' not implemented
Private Const IDTB_BOOKMARKS = 217            ' not implemented
Private Const IDTB_JUMP1 = 218
Private Const IDTB_JUMP2 = 219
Private Const IDTB_CUSTOMIZE = 221
Private Const IDTB_ZOOM = 222
Private Const IDTB_TOC_NEXT = 223
Private Const IDTB_TOC_PREV = 224

Type RECT
  Left As Long
  Top As Long
  Right As Long
  Bottom As Long
End Type

Private Type tagHHN_NOTIFY
  hdr As Variant
  pszUrl As String                            ' Multi-byte, null-terminated string
End Type

Private Type tagHH_POPUP
  cbStruct As Integer                         ' sizeof this structure
  hinst As Variant                            ' instance handle for string resource
  idString As Variant                         ' string resource id, or text id if pszFile
                                             ' is specified in HtmlHelp call
  pszText As String                           ' used if idString is zero
  pt As Integer                               ' top center of popup window
  clrForeground As ColorConstants             ' use -1 for default
  clrBackground As ColorConstants             ' use -1 for default
  rcMargins As RECT                           ' amount of space between edges of window and
                                             ' text, -1 for each member to ignore
  pszFont As String                           ' facename, point size, char set, BOLD ITALIC
                                             ' UNDERLINE
End Type

Private Type tagHH_AKLINK
  cbStruct As Integer                         ' sizeof this structure
  fReserved As Boolean                        ' must be FALSE (really!)
  pszKeywords As String                       ' semi-colon separated keywords
  pszUrl As String                            ' URL to jump to if no keywords found (may be
                                             ' NULL)
  pszMsgText As String                        ' Message text to display in MessageBox if
                                             ' pszUrl
                                             ' is NULL and no keyword match
  pszMsgTitle As String                       ' Message text to display in MessageBox if
                                             ' pszUrl is NULL and no keyword match
  pszWindow As String                         ' Window to display URL in
  fIndexOnFail As Boolean                     ' Displays index if keyword lookup fails.
End Type

Private Enum NavigationTypes
  HHWIN_NAVTYPE_TOC
  HHWIN_NAVTYPE_INDEX
  HHWIN_NAVTYPE_SEARCH
  HHWIN_NAVTYPE_BOOKMARKS
  HHWIN_NAVTYPE_HISTORY ' not implemented
End Enum

Private Enum IT
  IT_INCLUSIVE
  IT_EXCLUSIVE
  IT_HIDDEN
End Enum

Private Type tagHH_ENUM_IT
  cbStruct As Integer                         ' size of this structure
  iType As Integer                            ' the type of the information type i.e.
                                             ' Inclusive, Exclusive, or Hidden
  pszCatName As String                        ' Set to the name of the Category to
                                             ' enumerate the info types in a category;
                                             ' else NULL
  pszITName As String                         ' volitile pointer to the name of the
                                             ' infotype. Allocated by call. Caller
                                             ' responsible for freeing
  pszITDescription As String                  ' volitile pointer to the description of the
                                             ' infotype.
End Type

Private Type tagHH_ENUM_CAT
  cbStruct As Integer                         ' size of this structure
  pszCatName As String                        ' volitile pointer to the category name
  pszCatDescription As String                 ' volitile pointer to the category
                                             ' description
End Type

Private Type tagHH_SET_INFOTYPE
  cbStruct As Integer                         ' the size of this structure
  pszCatName As String                        ' the name of the category, if any, the
                                             ' InfoType is a member of.
  pszInfoTypeName As String                   ' the name of the info type to add to the
                                             ' filter
End Type

Private Enum NavTabs
  HHWIN_NAVTAB_TOP
  HHWIN_NAVTAB_LEFT
  HHWIN_NAVTAB_BOTTOM
End Enum

Private Const HH_MAX_TABS = 19 ' maximum number of tabs
Private Enum Tabs
  HH_TAB_CONTENTS
  HH_TAB_INDEX
  HH_TAB_SEARCH
  HH_TAB_BOOKMARKS
  HH_TAB_HISTORY
End Enum

' HH_DISPLAY_SEARCH Command Related Structures and Constants

Private Const HH_FTS_DEFAULT_PROXIMITY = (-1)

Private Type tagHH_FTS_QUERY
  cbStruct As Integer                         ' Sizeof structure in bytes.
  fUniCodeStrings As Boolean                  ' TRUE if all strings are unicode.
  pszSearchQuery As String                    ' String containing the search query.
  iProximity As Long                          ' Word proximity.
  fStemmedSearch As Boolean                   ' TRUE for StemmedSearch only.
  fTitleOnly As Boolean                       ' TRUE for Title search only.
  fExecute As Boolean                         ' TRUE to initiate the search.
  pszWindow As String                         ' Window to display in
End Type

' HH_WINTYPE Structure

Private Const SW_MAXIMIZE = 3
Private Const SW_MINIMIZE = 6
Private Const SW_NORMAL = 1
Private Const SW_SHOW = 5

Private Type HH_WINTYPE
  cbStruct As Integer                         ' IN: size of this structure including all
                                             ' Information Types
  fUniCodeStrings As Boolean                  ' IN/OUT: TRUE if all strings are in UNICODE
  pszType As String                           ' IN/OUT: Name of a type of window
  fsValidMembers As Variant                   ' IN: Bit flag of valid members
                                             ' (HHWIN_PARAM_)
  fsWinProperties As Variant                  ' IN/OUT: Properties/attributes of the window
                                             ' (HHWIN_)
  pszCaption As String                        ' IN/OUT: Window title
  dwStyles As Variant                         ' IN/OUT: Window styles
  dwExStyles As Variant                       ' IN/OUT: Extended Window styles
  rcWindowPos As RECT                         ' IN: Starting position, OUT: current
                                             ' position
  nShowState As Integer                       ' IN: show state (e.g., SW_SHOW)
  hwndHelp As Variant                         ' OUT: window handle
  hwndCaller As Variant                       ' OUT: who called this window
                                             ' The following members are only valid if
                                             ' HHWIN_PROP_TRI_PANE is set
  hwndToolBar As Variant                      ' OUT: toolbar window in tri-pane window
  hwndNavigation As Variant                   ' OUT: navigation window in tri-pane window
  hwndHTML As Variant                         ' OUT: window displaying HTML in tri-pane
                                             ' window
  iNavWidth As Integer                        ' IN/OUT: width of navigation window
  rcHTML As RECT                              ' OUT: HTML window coordinates
  pszToc As String                            ' IN: Location of the table of contents file
  pszIndex As String                           ' IN: Location of the index file
  pszFile As String                           ' IN: Default location of the html file
  pszHome As String                           ' IN/OUT: html file to display when Home
                                             ' button is clicked
  fsToolBarFlags As Variant                   ' IN: flags controling the appearance of the
                                             ' toolbar
  fNotExpanded As Boolean                     ' IN: TRUE/FALSE to contract or expand, OUT:
                                             ' current state
  curNavType As Integer                       ' IN/OUT: UI to display in the navigational
                                             ' pane
  tabpos As Integer                           ' IN/OUT: HHWIN_NAVTAB_TOP, HHWIN_NAVTAB_LEFT,
                                             ' or HHWIN_NAVTAB_BOTTOM
  idNotify As Integer                         ' IN: ID to use for WM_NOTIFY messages
  tabOrder(HH_MAX_TABS + 1) As Byte           ' IN/OUT: tab order: Contents, Index,
                                             ' Search, History, Favorites, Reserved 1-5,
                                             ' Custom tabs
  cHistory As Integer                         ' IN/OUT: number of history items to keep
                                             ' (default is 30)
  pszJump1 As String                          ' Text for HHWIN_BUTTON_JUMP1
  pszJump2 As String                          ' Text for HHWIN_BUTTON_JUMP2
  pszUrlJump1 As String                       ' URL for HHWIN_BUTTON_JUMP1
  pszUrlJump2 As String                       ' URL for HHWIN_BUTTON_JUMP2
  rcMinSize As RECT                           ' Minimum size for window (ignored in version
                                             ' 1 of the Workshop)
  cbInfoTypes As Integer                      ' size of paInfoTypes;
End Type

Private Enum Actions
  HHACT_TAB_CONTENTS
  HHACT_TAB_INDEX
  HHACT_TAB_SEARCH
  HHACT_TAB_HISTORY
  HHACT_TAB_FAVORITES
  HHACT_EXPAND
  HHACT_CONTRACT
  HHACT_BACK
  HHACT_FORWARD
  HHACT_STOP
  HHACT_REFRESH
  HHACT_HOME
  HHACT_SYNC
  HHACT_OPTIONS
  HHACT_PRINT
  HHACT_HIGHLIGHT
  HHACT_CUSTOMIZE
  HHACT_JUMP1
  HHACT_JUMP2
  HHACT_ZOOM
  HHACT_TOC_NEXT
  HHACT_TOC_PREV
  HHACT_NOTES
  HHACT_LAST_ENUM
End Enum

Private Type tagHHNTRACK
  hdr As Variant
  pszCurUrl As String                         ' Multi-byte, null-terminated string
  idAction As Integer                         ' HHACT_ value
  phhWinType As HH_WINTYPE                    ' Current window type structure
End Type

Public Type HH_IDPAIR
  dwControlId As Long
  dwTopicId As Long
End Type
Public Declare Function htmlhelp Lib "hhctrl.ocx" _
    Alias "HtmlHelpA" (ByVal hwnd As Long, _
    ByVal lpHelpFile As String, _
    ByVal wCommand As Long, _
    ByVal dwData As Long) As Long

Then, you need to add a procedure that will set the HTML file path:

Public Function SetHTMLHelpStrings() As String
    '// this presumes the help file is in the same directory as your app, and Main is the name of the window
    SetHTMLHelpStrings = App.Path & "\TestHTMLHelp.chm" & ">Main" 
End Function

To display the contents, use this code (from a form, otherwise you will need to change the hwnd value that is passed):

Public Sub HTMLHelpContents()
  ' Force the Help window to display
  ' the Contents file (*.hhc) in the left pane
  htmlhelp hwnd, SetHTMLHelpStrings(), HH_DISPLAY_TOC, 0

End Sub

To display the index, use this code  (from a form, otherwise you will need to change the hwnd value that is passed):

Public Sub HTMLHelpIndex()

  ' Force the Help window to display the Index file
  ' (*.hhk) in the left pane
  htmlhelp hwnd, SetHTMLHelpStrings(), HH_DISPLAY_INDEX, 0

End Sub

To display a specific topic, using a filename this code  (from a form, otherwise you will need to change the hwnd value that is passed):

Public Sub HTMLShowTopic(strTopic As String)

  ' Force the Help window to load a specific topic.
  ' The Help window will synchronize the
  ' Contents display automatically
  htmlHelp hwnd, SetHTMLHelpStrings(), HH_DISPLAY_TOPIC, strTopic

End Sub

To call it , use this code:

HTMLShowTopic "html\test_topic_1.htm"

To display a specific topic, using a context id  (from a form, otherwise you will need to change the hwnd value that is passed):

Public Sub HTMLShowTopic(lngTopicID As Long)

  ' Force the Help window to load a specific topic.
  ' The Help window will synchronize the
  ' Contents display automatically
  htmlHelp hwnd, SetHTMLHelpStrings(), HH_HELP_CONTEXT, lngTopicID

End Sub

To call it , use this code:

HTMLShowTopic 1000 '// 1000 = Context ID

At the moment, you cannot display the Search tab automatically from VB