Well.. first of all I wouldn't recommend doing it.
Guitar amps and speakers are meant to reproduce a certain frequency.
But CD's go all the way from 20hz to 20,000. You might get it louder but it's going to be very midrangy sounding, and there's a good chance the bass would crap out your speakers enough to actually damage them.

If you're intent on doing it though, you'll need an RCA stereo male plug to 1/4" mono female adapter and just a regular guitar cable.