How do you wire a car amp and sub?
Connect the subwoofer RCA cables to the amplifier.
Connect the left channel on the subwoofer to the left channel on the amplifier and the right channel on the subwoofer to the right channel on the amplifier. If there is a separate power cord for the sub, you may need to attach this to the amp as well.
How do you hook up amps and subwoofers to a factory radio?
The best way to connect it to a factory system is to tap into the stereo's speaker outputs for the amp's input signal. Then send the amp's outputs back to the stereo's harness, and on to the speakers through the factory wiring.