How do I convert my song so it's in the right format?
All music exported from GarageBand is exported to iTunes as an AIFF file. Because this is an uncompressed file and is quite large, we require that you convert the composition to MP3 or AAC. Follow these steps to convert your composition:

1. Export your composition to iTunes like you would for AIF files
2. Go to iTunes->Preferences and click the "General" tab then the "Import Settings..." button (Note: If you are using iTunes version 7 or lower, these settings are found under "Advanced" then "Importing")
3. Select either "MP3 Encoder" or "AAC Encoder" for "Import Using:", choose a "Setting" and click OK. We recommend "Higher Quality (192 kbps)" for MP3 and "High Quality (128 kbps)" for AAC.
4. Control-click your composition in iTunes and choose "Convert Selection to MP3/AAC" and iTunes will make an MP3/AAC file.
5. Control-click that file and select "Show Song File." This will open a finder window with your song.

We recommend moving this to a GarageBand folder in your Music folder (or any other folder) so you can access it quickly and easily.