69 valiant electrical gremlin turn signal and license plate light

Plug the socket and bulb back in. Turn on the park lights. Attach a jumper wire from the socket (maybe through the bolt holes) to a place on the car body. This should be a convenient place nearby, maybe an old bolthole, bracket or the bumper itself. You may need to try different locations as paint, rust and dirt may interfere with grounding. The bulb should light if you have juice, a good bulb and a good ground. Good luck.