The mirror channel leads to the back side of the gauge/switch panels. You may or may not find your truck was wired for lights with the wires behind the dash. My truck wasn’t wired, therefore I continued the wires thru the firewall to both headlight connections. If you take the cover off behind the air cleaners it gives easy access to fish the wires to the inside of the cab from the lights. I used a weather sealed plug with a wye off my headlights/marker/turn harness to avoid cutting my harness.