Well, when I bought my TRD
wing, when I went to hook up the 3rd brake light, the connector that was already in the back of the hatch didn't work, so I had to route the connector that was already connected to the third brake light, to the light on the spoiler.
Here's how you can unplug the 3rd brake light on the car.
1. Open the hatch.
2. Look up towards where the 3rd brake light is, and you should see a rubber grommet. It's just a rubber plug that keeps water away from your electrical connections. Reach in the hole that you unplugged the grommet from, and look for a connector. Unplug the connector, and you should be set.
Note, that in the kit that was supposed to come with your spoiler, there should be an adhesive piece of thin foam. You need to take that foam and wrap it around the connector that you just unplugged so that it doesn't rattle. Obviously, if you don't have the foam, just wrap it in something such as seran wrap. Just something to keep it from rattling.