How about a shot?
You need to Export your aircraft to FS2004 (or whatever) - in doing so you choose an existing model similar to the one you have made -
Once exported, the '.air' file & aircraft.cfg are there - ready made from the model you chose.
You can then edit the aircraft.cfg file to suit you model - simply do this in Notepad - should be fairly obvious stuff - but let us know if you have problems ...
Editing the 'air' file is far more complicated & something most designers tackle with great respect

- & probably not necessary with your 1st creation.

Simplicity is the ultimate sophistication. – Leonardo da Vinci