Just copy the amfe.gid folder to your problemtypes folder or make a symlink to the amfe.gid folder of your git repo
Open gid and choose Data -> Problem type -> amfe. Generate your mesh. If you want to export physical groups to AMfe, create so called "groups" in your GiD preprocessor. You can find groups as a tab next to the Layers. When you have finished, choose Files -> Export -> Calculation file. Choose a filename and click on ok. Afterwards you can import the resulting file in AMfe.