You will need an amplifier wiring kit with decent 8awg cable. Then you will need a line out converter so that you can connect your normal speaker wires into the line converter and then plug them into the RCA's on the amplifier
Pretty sure an Active Sub has a built in amplifier.
So you will need a power cable from the battery and a negative from the body.
You will need to find the ignition wire and connect that to the remote terminal. So amp powers up and down when you turn on/off the car. I am sujesting this method as there prob won't be a remote control cable in existing head unit.
There is prob no RCAs either, so you will need the line converters from the speaker wires.
Have fun pulling off all the trim to run your cabling!