You need to provide your own power and ground cable. Use 6-8 gage wire. You need to put the line fuse in the power line. The fuse holder will have a spot on both ends for the power cable. You just need to strip back some insulation and install the fuse holder. Your power cable will attach to the battery. You'll need a loop type lug connector to attach the power to the positive cable to the battery. You'll also need the same type connector for your ground. There's a ground in the trunk that your batteries ground ties to. You need to ground the amp at this spot. If you have any friends that have done this type stereo work, I'd get their help if you can or do a search in Google for amp installs. This amp installs pretty much like any other. You need to power it from the battery and ground it to the frame. Luckliy for you, both are right there in the trunk.
i reaaly need help installing the amp from sub thump and the instructions arent helping me at all.. how do u plug the rca cables into the amp( i have the same one your using) and how do you know wire is positive or negative.. and what does the smaller brown box part on the x3 do.. if you can answer any of these that would be awsome.. thanks