Download the WinHelp Common Dialog sample (attached below)

The Common Dialog control's ShowHelp method has always been Microsoft's recommended process for displaying WinHelp topics and structures. This small sample will show you how to:
Open the Contents and Index tabs of the WinHelp dialog
Display a topic using a Topic ID
Display a topic using a keyword

Note that there's no known method for opening the Find tab of the WinHelp dialog using the Common Dialog control. To do so, you'd need to use the WinHelp API.