go into your fusebox, ground the black wire and start sticking the red wire in the little holes. Depending on what you want it to turn on with (headlights, parking lights etc) you just find where it goes. I used a test light but you don';t even need to, just stick the wire into the slot and test to see if it works. For my 98 ex the upper right most one was the parking light wire



didn't even need to tap anything and it's stayed fine for awhile