Ok so there's already a thread for installing an amp and subs, but nothing about a powered sub, help?
What do I need to disconnect and connect to hook it up?
It's a Boss Bass1200
I have a 1999 with the stock sound system I believe

 

there are a few threads about powered subs actually
I installed a 15 inch JBL in the back of my car

What you need to do is this:

find a way to get the front passenger seat to come up so you can get to the factory subwoofer already there
OR alternatively get to the amplifier under the back passenger seat and splice the subwoofer OUT, not in unless you want the front sub disabled, no reason to disable it.
if going to the sub under the front seat route is selected like mine...
once you have access to that sub you will see there is 2 wires going to it
splice those 2 open and buy a Hi Lo converter and wire it to that while re soldering the factory sub wires back in
then you can use the RCA out on the HI LO converter and run a thin rca cable to the back trunk and run it to a sub there, but you must On whatever sub you choose to install Reverse the phase, there should be a switch on that, and your system will ROCK

dont please dont try splicing out any of the door speakers, they are NOT full range..

 

Ok so I have almost everything figured out, first off I don't need a hi lo converter because the amp can run on high input
I just need to know what the colors of the wires mean, help???
here are the colors of the ones that were connected to the stock woofer under the passenger seat:
black
yellow
dark green
light green

I just need to know which is which