Wiring up the F150LEDs running board light is quick and easy! Here are some suggested wiring guides to help you get started! Try making your splice connections at the rear passenger kick panel.
For your ground wire (black) splice the black/yellow as seen below in this BCM wiring guide.
For your power wire (red) you have a few options. If your first choice does not work you can remove the quick splice connector and retry the next wire. First splice the violet (purple) wire.
Another option is to splice the Grey wire w/ violet strip.
A third option is using yellow/green for power.
It should look like this.