Just be careful if you trim the insulation back, those wires are tiny! Props to you Keegan haha, I was too nervous to do that

 

I understand how to wire up the stock amp with the after market one. but im confused about the rca cable, the after market sub requires 2 of them. do i use 2?

 

Ahh I forgot about that. Mine were bridged so I only needed one cable. One is for the right side of the car and one is for the left side. You could start by using the right rear signal and see if both subs work. If not, then tap the left rear signal for the other one.