Exporting a Project to an m4a file to play on iTunes

I'm using Logic Express 8.0.2.

I have composed an arrangement of music with multiple tracks for different instruments. I know how to export an individual track as an audio file, but can't figure out if it's possible to export all the tracks into the one single audio file. Is this possible? Or will I need a 3rd part app to combine many audio files into one?