1. inside your Flight Simulator 9 main folder, find and double click the Addon Scenery folder.
2. Inside this folder, create a new folder with the name of your airport.
3. Inside your new folder, make 2 folders, one called scenery, and another called textures
4. Copy (or save directly from AFCAD) your airport bgl file inside the scenery folder you just created.

5. Start FS and go to settings, then to add scenery, then browse for your airport folder inside the Addon Scenery folder.

6. click ok, and close FS.

7 Re-start FS...and voila, your airport should be there now ready to be used.

enjoy

hector