If you plan on free-ranging chickens, they need to be three months or older so they're large enough not to be easy pickings for predators.
When you move chicks into a coop, you need to keep them cooped up with food and water so they get accustomed to their new home. After two days, try opening the coop door to let them explore. You'd best have a run that's protected from hawks and weasels, raccoons, foxes, skunks, possums, etc or you're sure to lose some.
The chicks will gather their courage to explore the "world", and will no doubt go in and out of the coop a lot due to their being uncomfortable with the large outside run. But they will prefer being outdoors when they get used to it.
The tricky part is getting them to go inside at night. Many do it on their own, but some need to be taught. You may need to get inside the coop and coax them inside with a light and treats for the first time or two.
