MP3 track in Garage Band ?

I moved some mp3s from windows to Mac and they're all instrumentals. When I open up Gaage band and try and get it to open one of the files it won't. The files are opaque, and I can't manually drag them either. Or use OpenWith.

I'm used to Adobe Audition/CEP where you can record over a track using multi-track....

Can I not do this in GB ?

To use an mp3, you have to first create at blank, new track... then you can drag and drop the mp3 onto that new track. If for some reason that won't work, it is likely that the only reason is the file is somehow or another protected and you won't be able to do this.

Thanks.

Is there a way to do it by File-> open or something too ?