Auvio audio cable with car charger for ipod and iphone with oldsmobile alero 2002?

I have an oldsmobile alero from 2002 and i want to be able to play music for my iphone 4s. The car only has a cigarette lighter port so i bough an auvio cable from best buy. When i plug it in it chargers my phone but how do i get it to play the music?

It can't, it won't.GM didn't install aux ports till '05.
Get a new stereo.