There are a few different ways to do this...
First you need to discover the tempo of the audio loop in Logic (or outside), change the tempo of the project to reflect the loops tempo, then I'd recommend you turn it into an Apple loop. Once you've done that, you can drag that loop from the Loop Browser into any project and it will match that project's tempo.
Here's a couple of articles to help (though this is explained in depth in the Logic 101 video course on this site too!)
Hope this helps