Logic Pro and Logic Express come with a large number of Apple Loops for you to use in your music compositions, but you can also turn any audio region—up to one minute in length—into an Apple Loop, or add loops to the Loop Browser from the Finder.
To turn a region in the Arrange window into an Apple Loop, simply highlight the region and choose Region > Add to Apple Loops Library. In the resulting dialog, you can assign search tags to the loop for better sorting. The loop file will be stored at ~/Library/Audio/Apple Loops/User Loops/SingleFiles.
To add loops to the Loop Browser from the Finder, simply drag an individual loop, or a folder containing multiple loops, onto the browser window. The loops are added to the Apple Loops library and indexed. If you use this method to drag a single loop to the Loop Browser, the loop will be copied to ~/Library/Audio/Apple Loops/User Loops/SingleFiles.
If you drag a folder of loops that are located on the same drive and partition as the Loop Browser, the loops will be left at their current location and an alias of the folder will be created in ~/Library/Audio/Apple Loops/User Loops. If the loops are located on a different drive or partition, you'll be asked whether you want to copy them to the loop library or index them in their current location (loops added from optical media will always be copied).
If you choose to copy them, the folder containing the loops will be copied to ~/Library/Audio/Apple Loops/User Loops/. If you choose to index them at their current location, then an alias to the folder will be created in ~/Library/Audio/Apple Loops/User Loops/.