Currently Being ModeratedJan 31, 2013 10:31 AM (in response to jb gband)
Export it to iTunes and then drag it onto the channel strip area in MainStage. This will create a channel strip with a "Playback" plugin instance using this audio file.
Currently Being ModeratedFeb 2, 2013 8:49 AM (in response to Blueberry)
Do you mean to convert it "mp3" and drag it in or leave it as Garageband track and drag it in