To use a Designer form, you must open a Designer library file, read in the data form, and then close the library file. The function that reads in the form resolves all the references to external variables (if you wish) and returns a pointer to the form. You then use this form pointer to act upon the form.
The fastest way to get a working prototype of your application is to use the Main Generator included in the Designer. The main() program that is generated automatically includes all the necessary header files, opens the correct Designer library, and reads in the main form and any associated forms, such as branching submenus or linked forms. It then calls fm_proc() to process the form. See the Designer User's Guide for more information.