I just pulled everything out of my car, including an entire 2nd battery setup.
Basically, you need either an Isolator or an Isolator Relay (a 200 amp relay). With the Isolator Relay you run one of the coil wires (coil wires are what turn the relay on) to something that gets power when the engine is running and the other coil wire goes to ground (bare metal spot on the car)
Then you take the other 2 posts on the relay and wire it like this:
1st battery pos terminal---->Isolator Relay---->2nd battery pos terminal
You would then ground the second battery's negative terminal to the chassis.
YOU HAVE TO USE BIG CABLES for everything except the coil wires, unless you want to set your car on fire.
I have everything you need except the battery (cause I cant ship that) for US$125 shipped. I would suggest, however, that you have a shop do it for you. You seem like a teenager perhaps and not so knowledgable about the proper way to wire stuff. You can destroy your car (flames, explosions, etc) if you don't do it right.