Outdoor Lighting For Deck
Conceptually, you would tap into the receptacle (or some other accessible source) run EMT (or some other suitable conduit, like Liquidtight) under the deck, pull THHW wire through it, run it up to where the lights are needed and install the lights. You would also need to route wire for a switch at each door, preferably inside the house. While certainly feasible, it would present a challenge for an inexperienced person. I recommend you pull a permit for the work, as not doing so can invalidate your home owner's insurance. Good luck!