1999 f-150, pop and lock system

Hi, I have a 1999 Ford F-150 I am currently installing a Pop and Lock Tailgate lock (PL8250)  on and I need some assistance in figuring out the wiring for it.

The truck locks and unlocks when ground is provided to the wires I fished through, as for the tailgate lock I don't know how that works, the instructions are not very detailed in terms of wiring, just how to physically mount to the taligate. If i try to connect the tailgate lock wires to the door wiring the locks (on the truck) won't lock/unlock when the button is pressed, So i am thinking i'd need a relay (hopefully only 1-5pin at most) in order to send the tailgate lock what it needs to operate, My question is for anyone who may know about these systems, What would I need to do to get this to work right?, How do I have to wire the relay(s)?

Thanks, Ace_boy2099

update: I gave up on trying to find the wires in the drivers door and just went to the pass door and ran wires from the door across the middle of the truck to the drivers side where the wiring was brought in, The wire colors were fine for the pass side but that isn't where I was looking to hook it up.