There is a group of wires that go to the door handle area. Probably like 4 or 5 wires to a connector housing. There is a grey wire with a stripe on the outer left most section of that plug that is the "trigger" wire. So basically you are connecting or splicing into that wire. It's most likely some low voltage wire that goes back to the control module "amp" that tells the boards to deploy. One tip is pay attention to how you route the wire when running the first section of wire through the interior of the door to avoid the window rails. The instructions are pretty good but they do leave out little details which I am sure they thought were common sense " ahem" for installers. It's really not too bad if you take your time but you will burn a day doing it. I also recommend a trip to auto parts store to get a set of non marring panel prys cost is about 15 bux and worth it as it helps to remove panels in a safe non plastic breaking fashion.