You can hook up your trailer wiring to the 12v output under the rear seat (many threads in Tesla forums about connecting to this for aftermarket sound systems). I used POSI-TAP connectors to tap into the tail light wiring (see https://smile.amazon.com/gp/product/B001MPW54G ). The tail light wire colors are as follows:
Passenger side: red=turn, yellow=lights, grey=brakes
Driver side: purple=turn, pink=lights, grey=brakes

This is the specific wiring kit that I used for my car https://www.etrailer.com/Wiring/Tekonsha/119190KIT.html