The wire it needs to plug into looks just like the turn signal lights, should be just sitting there unused with the rest of the taillight connections.
As far as the aftermarket light, you could cut the connector off of your OEM taillight/mud guard for the OEM plate light and just splice that into your new plate light and use that to connect to your wiring harness. That's what I did with my integrated taillight to essentially make it plug and play.
As far as the aftermarket light, you could cut the connector off of your OEM taillight/mud guard for the OEM plate light and just splice that into your new plate light and use that to connect to your wiring harness. That's what I did with my integrated taillight to essentially make it plug and play.