How to play my laptops itunes through my stereo?

i need to play my itunes on my stereo for a party im having tomorrow and im starting to panic cuz none of the things i bought are working. i bought an Aux Cable which a guy at walmart told me i could plug into my headphones hole and then into the headphones hole in the stereo and it would work, and the hole was too small in the stereo so i bought a portable audio extension kid with a big adapter and its still not working, when i plug the end into the stereo hole it turns off until i unplug it then it only plays from my laptop. is there a way or a cord i can buy to connect my laptop to my stereo to play my itunes from the stereo?