There is a small KEY in the Black Satchel that was provided to the new boat owner. There is a five pin harness on newer brake systems and the fifth pin has to connect to the reverse lights on your vehicle. If you do not have a five pin and are using a four pin, then turn it sideways while backing up and plug the blue wire pin into the brown on your vehicle. This will allow the solenoid to work with the parking lights on and allow you to back up. This is not for towing use, just in necessary situations.