really simple, you dont need after effects. a quick way is to make your text in ps
1 in a document the size of your video footage. black background with white text.
2 merge the layers
3 magic wand tool the white text
4 delete the white text you selected
5 you should be left with a black matte with a gap in the middle where the text was with transparent space where the letters were.
6 save as a .psd
7 import into fcp or the editing program of your choice
8 lay the footy down you want to appear in the text
9 lay the text matte .psd over top
bing bang boom render that n it should be good to go!
there are plenty of ways to do this, but thats always been a quick way that works for me
good luck