Direct wire or with a plug?
Simple way is to put a plug just under the lower lip of the cabinet and a wall switch in a convenient location.
You can leave a foot or so of wire sticking out the wall if you want to direct wire. Some AHJs will require BX or conduit for that though, so ask first. (My AHJ was ok with bare NM as long as it was fastened neatly to the bottom of the cabinets and the run was really short (~4-6" or so).)
If the wall board isn't up, then it's easy to drill holes in the studs to run wires. Don't forget a nailing plate to protect the wire through the studs.
You can pull power from a convenient outlet in the area. Whatever works. Personally, I like outlets on different circuits from lights. So popping a outlet breaker doesn't kill lights. Also, if it the lights are direct wire, they don't need to be on a GFCI, so either tap into a GFCI outlet on the *line* side or find a way for a new breaker. (again, check with your local inspector)
Do you want all 3 on one switch or separate switches for each or combination?
Bix box places have basic books on wiring for just this sort of thing.
Do you know the breaker / wire size from where you are going to pull power? You'll need to figure that out to buy the correct wire.