Introducing chickens is a time consuming process, just so you know.
Never just throw new chickens into an existing flock. The results can be catastrophic. You need to have an introduction period of at least a few days to a week, preferrably with the new ones fenced off so the "old" ones can't tear them to pieces. A 30 day quarantine is highly recommended as well (for adding adult chickens). Disease is easily carried from flock to flock, even on your shoes. I usually quarantine the new birds for at least 30 days, well away from the main flock, then put them in a pen near the main flock for a few weeks. You can then either divide your run into 2 separate sections or put the newcomers into a cage inside the run for a few days to let them get used to each other. Then I let them out to free range together for a few days/week, eventually they will fight it out and the new ones will blend in with the original flock.
If you have chicks, the general rule for adding new birds to an already existing flock is to wait until the newcomers are roughly the same size as the established birds. That way, they can at least defend themselves. Unacquainted chickens are going to fight, and unfortunately there is not much that can be done about it. It is just in their nature. But I would suggest that when you do finally put them together for the first time that you have the garden hose ready just in case anyone gets a little too out of hand. One quick shot of water should do it.
It would be nice if chickens could all just get along. Unfortunately, that was not programmed into their DNA. Chickens are cruel when it comes to outsiders until the pecking order becomes established. Once that is out of the way, peace should once again return to the kingdom.
Good luck & let us know how it turns out.
