Download Booklet for the task here.
Your Task is to listen to the video a number of times and then delete the audio and add your own track. You may not use 'songs' as a soundtrack, however you can use loops in GarageBand. The Booklet details how to add loops and effects etc.. but the newest version of GarageBand looks slightly different to the one in the booklet. Watch some of the following Videos to get some ideas of how they do it in the 'real movies'.