The cheap way: From the 1/8" mic port on your computer-1/8" male to 1/8" male cable with 1/8" female to 1/4" male adapter into the line out of the amp. Download the full evaluation copy of N-Track Studio(
www.ntrack.com ) **You can record, but you can't burn anything.** That'll get you started. This will only cost you about $5 for the cable and adapter. The quality isn't great, but it works.