Use Help from the Apple menu for more details. Failing that:
In short:
1. Run this application
2. Use Open… to open the AppMaker application
3. Double-click on a template name to view it
4. Use the Extract button to extract templates to text files
5. Use the edit box and the Show button to change templates
Why? So you can edit templates to your liking. The best way to edit templates is as text files, in a text editor. That way, you can see formatting (including tabs). When you're all done, use Rez or SARez to merge your changes back into the AppMaker application. If I were you, I'd create my own 'Lang' resource and choose a new type, rather than write over the existing types; that way, if you have problems, you can more easily compare your template-generating code to stock AppMaker template-generated code.