How can I power this?
Simplest thing is to buy a 14ga extension cord long enough to reach your receptical (a decent "shop" cord not a lamp cord). Cut the female end off and discard, then strip the wires back. Remove the knockout in the light fixture and insert the appropriate cable clamp (commonly called romex connecter), then, using wire nuts, connect white/white, black/black, green to grounding screw on fixture . Support the cord with a few staples, and plug in.