rmaki! please read the FMGo developers guide. There is no "f1" and there are no tool tips for iOS. You can "popup" another window, but on the small screen it's probably going to cover the entire "screen".
Your first step is the developers guide, though.
One option would be to put a help button on the layout somewhere that when pressed runs a script to populate a custom dialogue with your help text.
You could also potentially turn your field lables into buttons to give specific help for individual fields.
If I was going down this track I would probably look at setting up a help table and then use script parameters to find the record to display in the custom dialogue to allow easier maintenance of the help text!
Yes, Dialogs are different on the iOS. Check that Developer Guide!!
semplicity is the best Help for the user.
So the GUI shold be essential, simple, beautiful to see and to work with...