Basic GarageBand help

Hello - Im new to garageband and have a few basic questions.

What I need to do is take a rough mix recorded at a different location and import it into garage band to split tracks and EQ (if poss). I couldnt figure out a way to do it with the track saved in Itunes. the initial track is on a cdr and I assume it is an mp3 file. Any help is appreciated.

To clarify:
By splitting tracks I mean song 1 - song 2 - etc, not seperating drums from guitar or vocals.

open a new grage band window and click tracks at the top

then click new basic track (or something similar, this is from memory)

you will then have a blank track where you can click and drag your mixed mp3 from itunes straight to it. From there you can cut and copy and paste the track up to your hearts desire (there is a little scissor icon near the bottom left which will help)