It's made by Westfalia. It comes in a nice case and has a lock with 2 red keys.
Picture 3 shows in which position must be the knob in order to insert it.
There is a plastic panel under the car, twist the 2 screws with a coin and the panel pops right out.
Remove the insert from the hole.
Insert the hitch all the way in until it clicks into position, at which position you can turn the small red key 180 degrees to lock and remove it.
Fairly standard. Last pic shows the electric socket.