A question to the mac heads out there.

Ive used imovie a few times, but now I am getting this annoying issue with having two tracks combined as one.

I want my film clip as one track and the music as the second track, that way the film can be cut and edited to the mood of the music.

At the moment as soon as I drop my music track in, it combines with the film track and stops where the film clip stops.

How do I get it back?

Is this clear or a bit confusing?