My Puma wasn't pre-wired. I put in 2 8g wires. I started from the inside, laying down on the bed and feeling where the roof/ceiling structure is with my fingers. I wanted to make a hole as far forward (toward front of truck) and as close to the lift panels as possible. That way I could run my wires along the backside of the lift panels... same as what the factory does. I made the holes in the ceiling liner using a hot soldering iron tip. This makes a clean hole that is self-sealed and won't run. I moved some of the insulation aside with a small screwdriver and then made the first drilled hole with a 1/8" drill, checking to see where it came out on top.
Where on top was important too, as I had a specific roof mounted gland in
mind. It's about 4" square in size.
Once that small hole was made, I enlarged it to 1/2" and made another matching hole. These were lined with rubber grommets and the wires pushed through. Connection to the MC4 wires coming from the solar panel were made by cutting off the MC4 connectors and using wire nuts to join the wires. Used 3m 4200 to seal everything up and 4 #8 screws for good measure.
Back inside the camper, the wires are taped to the back of the lift panel using Gorilla brand duct tape, and then run behind the carpet for bit, then behind the 4" x 48" trim along the length of the bed area. There should be a yellow wire there already for the ceiling lights and fan that you can follow along.
Once you get the wires down into the area of your battery box, there are more things you will need... controller, monitor, etc