What you bough from your friend was a set of home theater speakers. You need to purchase a receiver to power them that you would hook the speakers to. You would then hook the laptop to the receiver and that is how you would get sound. Now in order to get a little better sound I would even recommend an external sound card for your laptop to then hook to the receiver as that will more than likely sound better then simply running a cable from your headphone out.
If you have don't bother with the external sound card you would need a 3.5mm stereo to Left Right (red and white) RCA cable from the headphone out to one of the inputs on the receiver and then the speakers hooked to the receiver.
If you get the sound card depending on the outputs it has you would use the best one it has, more than likely a digital audio out of some sort to the receiver.
Good luck, You need to spend more money, sorry.