From what I understand they need to stay in the coop a week or so. Someone more experienced will chime in here hopefully, but a week and I think they'll be "homed in" to the coop. And, yes, they should then return to the coop at night.
from what i have read on this forum, only a couple of days, but I kept my ladies in the coop for a week just to make sure; I did not want to be chasing them around with a fishing net in the dark.
I have read on this forum of people moving their coop 50 ft away or so and the chickens would go to ths spot the coop used to be and sit on the ground; pretty strong homing instinct.
how old are your chicks? how long have they been in their coop? Ours were just a few days short of 6 wks. We left their heat light on in the coop until they were 6 wks and fully feathered. It took just 2 nights of us putting them in the coop before they started going in on their own. Right at 8 p.m. As for free ranging. Ours spend most of their day in "their" fenced yard. However we have been allowing them more and more time out. Returning to their yard/coop area has been a breeze for us. I just call them and they come running. Of course, they know that I have some special dinner type snack. Oh they can be cought so easily.
It will help if you will teach them to come to your call. Decide on a sound or phrase, use it and offer a treat. Does not take them long to learn the sound means goodies. Then you can use this to call them to the coop.
A light in the coop for a while can help, too. A battery operated closet light or flashlight will do. Once they dependably go in a at dusk, you won't need a light any longer.