Go to the Electronics, Audio, and Accessories subforum and there is a lot of info there as to how to wire it all.
It is MUCH easier to tap into the 12 volt connection under the back seat on the drivers side. My power wire is about 7’ long and no having to find a grommet or drill to get it into the cabin.
There is a long write up in my system. It cost me $250 total doing everything myself, including building my own box for a 10” subwoofer under the drivers seat.