how do you wire the remote wire to add an extra amp for a sub on a pontiac grand am 2004.

I've always grounded straight to the metal of the vehicle. Self tapping screw directly into the metal in the trunk. Just be careful where you do it. Don't do it through carpet or into the body or gas tank. Just find a nice solid piece of exposed metal. The remote wire can actually be any 12v power source. I normally jump off of the power antenna in the trunk, this way the amp turns off with the radio. But any 12v will work. You can actually jump directly off of your power wire going to the amp, but you'll need to put a switch on it so you can turn it off when not using it. This is scary if you forget to turn it off. Dead car.