Tough to help without you being more specific. If you just want to listen to tunes, get a good set of in the ear 'phones, plug them in to whatever your source is and rock and roll. If you're interested in getting a GPS, radar detector, and tunes connected, there are options for that as well.
I've got a Mix It 2 that connects my i Pod together with my GPS and radar detector which are set up to over-ride the i Pod. I've got separate power set up for the Mix It and my i Pod, so I can listen whenever I'm riding.
John