After a lot of research I found out that you really need to let the chickens get to know each other safely with a barrier so they don’t hurt each other.
Have a small cage that your new chicken or chickens can be in with fresh food & water. This keeps them safe and lets the other chickens get to know them.
There will be pecking orders established so some pecking is okay. Just watch to make sure they aren’t fighting for more than 20-30 seconds, drawing blood.