In general a file that is displayed in Aerofly and FMS (*.geo) fly in FMS.
Also the sound (*.wav) and the textures (*.bmp) are imported.
Only the flight characteristics must be copied from another FMS model and then be adjusted.
The easiest way is:
Copy the 3 files
1. model name.geo
2. model name.wav (if existing)
3. model name. bmp (if existing)
to the FMS directory. Then copy the .par file from a similar flying model of FMS into the folder where your new Aerofly model is located and overwrite the Aerofly .par.
If you have the model files extra300.geo, estra300.bmp and estra300.wav copied from Aerofly to FMS\Model, copy e.g. the SU_26.par from FMS to extra300.par.
This file “contains” the flight characteristics of the model. After you have renamed it, you can load the extra300 in FMS. If you open the .par file in a text editor you can adjust the values and change the flight characteristics of the model.
NOTE: Even if you fly a glider without sound you should create a “model name.wav” file. Just take any .wav file without sound and rename it. FMS might have problems with a model without an according .wav file.