This is where you enter the next realm of modeling.

What I do.. is to start with an air file that's similar. Like, if it were a Beech Bonanza, I'd probably use the Mooney air file.

You can go in with an air-file editor later, to clean it up.. but first you need to write an aircraft.cfg file. THIS is where you start to give your creation its individual, unique traits.

If all you want to do is to see it fly in FSX.. you can use the aircraft.cfg file that matches the air file.. but it will fly like that aircraft.. AND sit on the ground as though it were that aircraft.

There's a whole lot to learn here..  Spend some time studying the SDK (aircraft config file section) to get started.. then when you hit a wall.. come ask.. we'll be here