I'm pretty sure it mounts in the trunk, just like most subs. And I'm pretty sure that there are no running wires to it since its strictly an aftermarket toyota dealership part, unlike fog lights, which one some cars that don't have them still come pre-wired for them (like mine did). touringcamry is almost correct, but you're thinking of the wrong part. haha. Under the passenger seat is where the factory amp goes.
So basically, you're going to have to buy the wires (and amp, unless you already have one) from Toyota.