6 Hens and 1 Cock.
I take this to mean they are adults, not babies, especially since you have experience with other types of birds. You'd be surprised at how many on here would call day old chicks hens and cocks. Age is important.
How long to keep them locked up? To me this depends some on what your garden looks like. Is it wide open or fenced? Roofed since they can fly? Can they get out? Different gardens can look way different. They can be creatures of habit. If they get used to sleeping in the coop they should return there every night at dark. If you lock them up until they get in the habit of sleeping in the coop they will probably return there every night. I say probably because with living animals you don't get guarantees. If they are used to sleeping in trees where they come from and your garden has trees it may be harder to train them. Usually a week is enough.
If your garden is totally enclosed and they are fairly easy to catch another option would be to just turn them loose in the coop/garden and see what they do. If they do not go into the coop to sleep on their own they are usually pretty easy to catch after dark (assuming you don't have lights in your garden so they can see you). Toss them in the coop every night after dark. They should soon get the message and start going in on their own. There are two reasons you may need to know this. If your coop is too small to keep them locked in there for a week you may have to do something like this. Or they may not go into the coop at dark on their own no matter how long you leave hem locked in there. I regularly move 5 week old to my grow out coop and pen. No matter how long I leave them locked in that coop before letting them into the run they don't go back in there at night. I have to use this method to train them to sleep in the coop. I think it's because my grow out coop is elevated. Although these 5 week old chicks can fly better than adults they are not yet used to roosting, so they like to sleep in a group in a low spot. I think locking adults in the coop for a week is likely to work, but just in case you know the procedure.
One purpose of locking them in the coop is, if they are adult and laying, to try to train them to lay in the coop. If they are free to select a nesting site they may easily choose one in your garden. Again, they are creatures of habit. Once a hen gets in the habit of laying in one spot she tends to return there to lay. A week should be enough I suggest putting a fake egg (I use golf balls) in the nests to show them that the nests are a good place to lay.
As Cmon said, here in the US Rhode Island Reds are production birds and have been bred to hardly ever go broody. A broody hen is not laying eggs and disrupts the flock, plus requires special handling. They use incubators and brooders to hatch and raise chicks. It doesn't take that many generations of making going broody a fatal condition to mostly breed going broody out of a flock. You can still have exceptions but with Rhode Island Reds not many. I would expect South Africa to be similar to the US in this. You can talk to the people where you are getting them about this, it is possible they have bred them to go broody fairly often. It can be done. Even hens from breeds known to go broody don't always go broody. Each is an individual. If you plan on hatching eggs from them an incubator may be in your future.
I take this to mean they are adults, not babies, especially since you have experience with other types of birds. You'd be surprised at how many on here would call day old chicks hens and cocks. Age is important.
How long to keep them locked up? To me this depends some on what your garden looks like. Is it wide open or fenced? Roofed since they can fly? Can they get out? Different gardens can look way different. They can be creatures of habit. If they get used to sleeping in the coop they should return there every night at dark. If you lock them up until they get in the habit of sleeping in the coop they will probably return there every night. I say probably because with living animals you don't get guarantees. If they are used to sleeping in trees where they come from and your garden has trees it may be harder to train them. Usually a week is enough.
If your garden is totally enclosed and they are fairly easy to catch another option would be to just turn them loose in the coop/garden and see what they do. If they do not go into the coop to sleep on their own they are usually pretty easy to catch after dark (assuming you don't have lights in your garden so they can see you). Toss them in the coop every night after dark. They should soon get the message and start going in on their own. There are two reasons you may need to know this. If your coop is too small to keep them locked in there for a week you may have to do something like this. Or they may not go into the coop at dark on their own no matter how long you leave hem locked in there. I regularly move 5 week old to my grow out coop and pen. No matter how long I leave them locked in that coop before letting them into the run they don't go back in there at night. I have to use this method to train them to sleep in the coop. I think it's because my grow out coop is elevated. Although these 5 week old chicks can fly better than adults they are not yet used to roosting, so they like to sleep in a group in a low spot. I think locking adults in the coop for a week is likely to work, but just in case you know the procedure.
One purpose of locking them in the coop is, if they are adult and laying, to try to train them to lay in the coop. If they are free to select a nesting site they may easily choose one in your garden. Again, they are creatures of habit. Once a hen gets in the habit of laying in one spot she tends to return there to lay. A week should be enough I suggest putting a fake egg (I use golf balls) in the nests to show them that the nests are a good place to lay.
As Cmon said, here in the US Rhode Island Reds are production birds and have been bred to hardly ever go broody. A broody hen is not laying eggs and disrupts the flock, plus requires special handling. They use incubators and brooders to hatch and raise chicks. It doesn't take that many generations of making going broody a fatal condition to mostly breed going broody out of a flock. You can still have exceptions but with Rhode Island Reds not many. I would expect South Africa to be similar to the US in this. You can talk to the people where you are getting them about this, it is possible they have bred them to go broody fairly often. It can be done. Even hens from breeds known to go broody don't always go broody. Each is an individual. If you plan on hatching eggs from them an incubator may be in your future.