Every time I have added chickens (4 times), I wait until it's dark. Then I put the new birds in the coop, right on the roost. Next morning, I release the birds at the regular time, but not any later. The old birds wake up, see the new birds and everybody gets a big feed. "Hey, I don't remember you, but you're here so I guess it's ok." Then they have the day to sort it out. I've never had a new bird not figure out where to go to sleep (moving the coop is a different tale). It takes a few days, but adding 5 who are already a flock should work out easier than just adding one.
They're going establish who's going to be #1 hen and the subordinates all the way down to #last regardless of what you do. Put the new girls on the roost and they should have it worked out before you get out to check on them in the morning.
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