Running board lights?

Ok so I have a 2004 Explorer with the metal, rounded bar running boards, NOT the plastic kind that are molded to the car. I'm trying to figure out a way to stick some white LED strips to the underside of my running boards and wire them up to the puddle lights so they come on when I unlock or open the doors just like the puddle lights do. How easy of a job is this? I'm fairly experienced with wiring but I don't know where/what to tap into. Please help!

 

[BlkSquad]

Sounds like the easiest way would be to tap into the puddle lights using a relay. Would it not be better to put the LEDs above the step rails instead of under? Seems like putting them underneath there is asking for them to not last very long.