Hi dhasdell, and welcome to the community!
You can find the FMB in the "Extras" Option, in the main menu. Some tutorials can be found here, but beeing you, i`d sign up at the ATAG-Forum and ask there (
http://theairtacticalassaultgroup.com/forum/forum.php), because since the official support for this game was given up, the ATAG-Forum seems to be the biggest knowledge-base.
If you have plans to build online-missions, you are highly welcome to do that. The community needs more mission-builders
Also, I recommend to download the Team Fusion patches from there!