Synchronizing two audio tracks

Hi, I have two audio tracks, one instrumental and one vocal. I want to attach the vocals to the instrumental. When I import both files to the garageband program I can't get them to synchronize. In other words I can't get the vocals to match up with the instrumental track. Is there any way to auto synch, or anything that can help me synch these two tracks. If anymore explaining is required let me know. I use garageband 3.0.4 if that info helps.