To be honest if you are unsure what you need you may be in over you head on this one. Starting from the battery on the X you need a good size large wire gauge battery terminal binding clamp. With this type of system you want to run at least 8 gauge for amp power. 4 gauge is better. You will also need to install a 1 to 1.5 farad capacitor to prevent voltage sags that will drive your amp to clip at musical peaks.
If the amp or head unit does not include an electronic crossover, you will need and outboard crossover to blend the sub into the rest of the system. Of course with the power wiring you will also need fuses, fuse holders (power distribution block), at least one if not more RCA cables of required length, and a good close ground point on the frame wired with 4 gauge minimum.
This is what comes to mind off the top of my head but I may have forgotten some things. Best bet is to find someone who has done similar installs. Good luck with your system.

O well i guess thats not going to happen.

Anyone have any advice on how to go about this?

I think i understand it now since i found a helpful site. So i need a wire from the battery, wires to go from the HU to the amp, a grounding wire, and a wire to connect the amp to the sub. If thats right, how do i get the power wire to the rear seats? And is there a recommended place to put the grounding wire?

Thanks