There are a few options. First, if you already know the tempo of the track(s) you bounced, and that tempo is constant, you can set the tempo and then line it up. If the tempo is not constant, you can use the "beat mapping" capability. The best way to do this is to "detect transients" and then drag the beat line down to where that transient to have Logic match it all up. It's too much to explain here, but once you get it, it is a really cool feature. Here's a BLOG post on that: http://www.jamesbiss...apping-in-logic
Beat mapping is an excellent tool that is easy to use once you really get how it works, but like most things in Logic, it looks a little daunting at first. Just set aside some time to play with it and the transient detection feature.