Here are tutorials to help you edit audio using various audio editing programs:
A very quick 2-1/2 minute video on Adobe Audition
AMAZING tutorial offerings via UC Berkeley Graduate School of Journalism's KNIGHT DIGITAL MEDIA CENTER
Garageband:
Soundtrack Pro:
Instructions for Audacity are in the Course Reader, however the KDMC Audacity tutorial is very useful:
And there is also an EXTENSIVE wiki on Audacity created by the people responsible for providing us the latest versions of the program - the Audacity Team.
Be sure to note that Audacity requires the LAME encoder to compress your finished files down to .mp3