Putting the factory style puddle lights under your mirrors will be better than having nothing at all, but not as bright as an LED strip. If I didn't already have puddles to retrofit and was looking for the simplest way possible, I would have gone this route.
2007-2014 F150 Daytime BrightLites LED Puddle Lights (800 Lumen) PUD-CREE They have a 380 lumen set as well but I figure for $19 extra, why not jump to the 800 lumen. If you order them from Ford, it looks like you'll be spending at least $6o plus shipping anyways.
Buy 2013 Ford F-150 Parts | FordParts.com. As far as the wiring, I'm not to sure on that but it seems to me that you could just test the wires in the mirrors and figure out which one gets hot when you unlock the truck, then tap into that one. If you need help getting the mirrors apart, there are several threads on here that will help you with that. Just use the little search bar in the top right corner and look for "mirror turn signals" or "puddle led" or... you get the idea. Another option depending on how accessible it is for you is to just go to a junk yard and pull a set out yourself, or just grab the whole mirror set up so that way they are already wired and in place.
