If buying vaccinated POL pullets from a known
source then you can mix your new hens straight
in with the others, in the chicken coop at bedtime. If you collect your new birds during the
day then put the new hens either in the hen house with the door shut, in
a seperate run or in a crate in the main run during the day - don't
forget to give them food and water! Then put all the birds in the chicken coop together at bedtime. The next morning let all the birds out of the chicken coop, but
always put an extra feeder and drinker in the hen house or run for a few
days so the new birds can eat away from the older ones without being bothered or bullied.
If buying from an unknown source such as an auction it is best to keep new chickens seperate for 3 weeks in case they get stressed during the move and show signs of illness which can bring a disease to your hens in your existing chicken coop. After this move the chicken runs next to each other or put all the hens out in the garden together so they get used to each other for a few days before putting them all to bed together one night in the hen house. There will be some fighting but the more space they have the better. They should settle down in a few days.