Now you feed it down the passenger firewall.
That's from under the truck with the loom coming down the back of the wheel well.
Next I ran it down the truck on top of the passenger frame rail, securing it with long zip ties.
When you get to the back of the truck, you may run out of plastic loom. You can easily buy more from any hardware store, but you don't need it.
Now that you've made it to the back of the truck, those 5 wires (two blacks, two reds, one white) are going to split. one red/black pair will go to the passenger side light, the other pair to the driver side light.
The white wire is your reverse wire. This you need to tap into the 7 pin trailer wiring harness.
Your 7 pin should have the reverse power in the middle wire.
Unwrap the tape around the loom to gain access to the middle wire, tap in, then wrap it back up.
Well there you go, those were the basics of the wiring. From here it's up to you to customize the application to your needs.