Do what Nigel said with the 1/4 and plug that into your sound card. You will want a recording program (I use cool edit pro and love it). Then you will want to play your song on your board. Record in layers if you can. It just gives you the upper hand when you add effects. You will want to use a mixer along with it to get the EQ's right. When its complete just save as an mp3 or whatever and your done.

Phil