The Apple documentation is from the 10.6 era and appears to be not correct for the modern OS. I have the help book prepared as a html document. What needs to be done to take this html document (html text and in the same directory a directory with all the image files. In Firefox the html document displays correctly. What modifications are necessary for the html document? And where do I lace this in the application bundle?
You need to create a help book. Here is the documentation.
It is very old, but it still works mostly. In modern versions of macOS, help will open using the standalone "Tips" app. In older systems, the help will be integrated into your app.
A help book is nothing more than a bundle of localized HTML resources and assets. It is a little tricky to get it integrated into an app, but no more so than anything else Apple does. And since it is a stand-alone bundle, you can view the help documents using Apple's default help viewer, an external web browser, or your own integrated help display. I recommend against using anchors, however. That seems to be one help feature that was broken a few years ago. Instead, break your help up into smaller pages.
And if you're working in iOS, you re-use all the same content and architecture. iOS doesn't have the same kind of help architecture, but you can easily display your help content in a web view.
You might find the following article helpful:
https://marioaguzman.wordpress.com/2020/09/12/auth/