once they are past quarantine keep them in a separate cage inside the run for about a month. if you free range them then they can be let out all together but do not lock them in the same coop at night. When you do add them into the coop at night change the coop so it isn't the same look. this way your normal hens wont feel like someone is in the area. when i first added hens to my flock there was some fitting and i thought it would be ok.about 4 days in i went out to cheek on them and found two very scared hens in a corner with a lot of feathers missing. after closer look at the inside of the coop i found blood every were. i will never add hens straight into my flock ever again. if you want to add new chickens get some that are raised together this way they will have a friend and it wont be so stressful. if you add chicks do not add them until they are at least 12 weeks old and have seen each other since the chicks were brought home. an adult hen can kill a smaller bird with just 1 peck.