Download the music onto your Mac's hard drive. If you are already working with an .mp3 or other music file format, continue to section two. Otherwise, find the output jack on your digital recorder and connect the cables accordingly.
Connect the other end of the recorder cables to your Mac's mic input.
Open Garageband and select "New Track."
Push record within the Garageband software, and push play on your digital recorder.
Push stop when the song is finished playing. Your song now be stored as a digital file within Garageband.
Use the cursor to select the editing pane, which looks like a pair of scissors.
Notice the wave version of your song in the editing pane. You can select different areas of the file by running your cursor along the wave and highlighting a certain area.
Highlight and press "Delete" to delete a section of the song.
Highlight a section of the song, press cut and then paste where needed to loop sections of the song.
Trim the beginning and end of a music file by putting the playhead at the beginning or end of a track and moving it in or out to expand or reduce the track size.
Save the file and give it a file name after you have completed your edits.