I got it figured out, thanks for the help. I thought that in order to set the scratch disk (this is before I did my research) I needed to “choose” my external drive for more than just the scratch disk tab. Guess I should have read titles like “search folders”.
Anyway my next question has to do with soundtrack pro. When I open my project in soundtrack, effects that I made on audio in FCP don’t show up (changing the speed for instance). Also, I can’t seem to get the work that I’ve done to move back into FCP after I’m finished in soundtrack.