I just purchased speakers, a sub and a receiver and i'm new with all of this so I'm kinda struggling. The speakers all hook up fin eot the receiver but the sub out plug is where my subwoofer goes but I only have thw two bare wires coming from my subwoofer and not a plug, what do i need to get in order to put my two bare wires from my subwoofer into my sub out plug on my receiver?