It's easiest to just completely remove the amp from the car.
Then, just plug the wiring harness that connects to the JVC's speaker outputs to the factory harness. IIRC, it connected on the left side of the amp.
It sounds like you've got the power, ground, etc... connected correctly already.
BTW, the wiring harness (by design) is only able to plug into the correct factory harness. So, it's really a no-brainer as to what it plugs into.
