Editing pre-recorded tracks with Garageband 10.0

I currently record myself playing guitar using quicktime in .mov format.

I utilize garageband 10.0 (newest at this time) to edit the audio (clean up noise, add reverb, etc.)

I notice that the left track has all the information I want with the right track having some other information.

I want to edit so that the left track comes out of both the right and left speaker when it exports to disk.

Can anyone provide some insight on how to do this?