I don't want to sound condescending here...so bear with me.
First get your self a tutorial from the editors depot!
Second all files (.ext,.csv etc....) talked about are in your mission file.... that is C:\Armedassault\missions (or what ever it is... for me it is still Codemasters\operationflashpoint\users\Kendo\missions) the .ext file is the description that loads all basic information about the startup screen, weapons in the breifing, sounds and respawns.
If you wish to spawn units in the mission you can make a script to do this... .sqm file (text file with your scripting commands).
For a noob start to scripting it is best to take someone else's script and edit it...
I don't know if AA has a spawn script in the ed depot but OFP has loads... best go look there first!
Kind Regards
& good luck
Kendo