Recording with Garage Band Inspiration/Technique

So I have this iMac and finally got a new bass. I'm plugged in this very moment. Going through all of the drum/percussion loops/kits. I have ideas for bass lines for songs but just don't know what to piece together with the loops. Or if I should do the loops first or bass line on a click track. I dunno...never done this before, never had this stuff available to me. I've always been a plug and play with the band and someone else took care of the recording.

What do you guys do? Tips, tricks, etc.