LED's are actually a diode that passed voltage only one way. So you hook up the two wires to 12v and ground, and the way that they light up is the correct way to wire them into you harness. Now the neutral and oil lights, go to the switch with the negative side that you determined go to ground. The other side goes to 12v. It isn't that hard to figure out, and if it doesn't work one way, swap the wires around. You will figure it out.
Charlie