The idiomatic expression "to turn out the lights" means to extinguish or put out a light, either literally by switching off an electric lamp or figuratively by ending something. Full definition
Or, he can listen to a relaxation app before turning out the lights. (childrenshospital.org)
Do simple things like turning out lights when you don't really need them, not letting the air conditioning or heat run with your windows open, and so on. (relevantmagazine.com)
He picked up laundry, brought me snacks, shared his toys, and turned out lights at night. (babycenter.com)