If you don't understand wiring in general, and trailer wiring in particular, this is no place for guesswork and on the job training. Improper wiring can disable your Spyder. I have never seen any lights that didn't have ground wires, so adding a new ground wire run to the Spyder, while necessary, is not the answer. The exception would be if you have already wired the grounds (usually black) on your lights to the trailer chassis...that will have to be changed. They would have to be connected to a ground wire which runs to the trailer connector, and connects to a corresponding ground pin on the Spyder connector. BTW, trailer wiring is usually color coded and sequenced in a certain order in the connectors. If you are unfamiliar with all this, get some instructions or some knowledgeable help...or visit a trailer shop.