When it's time to move the chicks from brooder to pen and coop, do they need to be trained to go into the coop for the night?
If you want them to sleep in the coop and they were not brooded in the coop, almost always yes. Some of us brood in the coop so it is not usually an issue but for about everyone else, they need to be trained.
How is the transition handled? Do you put them into the coop first for the night and let them figure out how to get in and out into the pen? Will they go into the coop on their own when evening comes or do they require some inducement?
It is handled different ways. Many people house the chicks in the coop only for one or more weeks before they are let into the run. The coop is usually so much bigger than the brooder that they can handle being locked in there without being crowded. Sometimes, not always but sometimes, that is enough to train them to put themselves to bed whenever it gets dark. To me that is the first thing I'd try.
That never works for mine. I think it's because I have an elevated coop I'm trying to train them to sleep in. I don't have this problem with a ground level coop. Until they learn to roost mine like to sleep in a group on the ground. That's what my broody hens do with their chicks until she takes them to the roost. I think it is instinctive for them to hide in a low spot in a group. Mine always try going to sleep in a group under the pop door.
So every night after it is dark enough for them to put themselves to bed, which makes them easier to catch, I lock them in the coop. If I am consistent they get the message. My broods are typically around 20 chicks. Sometimes they all get the message pretty quickly, just a few nights. A couple of times It has taken three weeks before the last few got the message. Most broods totally catch on after a week. Each brood is different.
How much light gets in your coop, hopefully you have a window? If they cannot see inside the coop to go to bed when it starts getting dark they won't. Some people have helped themselves with this by putting a small light in the coop until the chicks are inside. I have a window.
Some people lure them inside the coop, usually with food, before it gets dark and lock them in. That's probably less work than physically putting them in after dark but you won't know when they will go in on their own. It's just how people choose to do it.