iberia346-
Open the .cfg file, and look under the list of programs that it gives you to open it with and choose "notepad"
Notepad is like a basic word processor, and in the case of FS aircraft (AI or flyable), you can view or edit all of the flight dynamics and information with it.
When you want to add an aircraft to AI traffic, you need to add it to something that is called the aircraft.txt file. This is one of three parts of the "traffic.bgl" file, which is the main database for every single AI plane and flightplan in FS. To open this file you need TrafficTools, a free program that sperates these files.

I highly recommend this easy tutorial on AI traffic and TrafficTools:
http://www.jetdoc.com/HLP/helptt2_1.htmlI know this can be confusing, but I hope this helps!
