A lot depends on your set up, and how you have it set up. Do you have multiple feed places? Are the feed places set up so that a bird eating at one, cannot see a bird eating at another? Do you have mini walls, and hideouts where birds can get out of sight?
What has worked very well for me, is to let your original birds out of the coop/run for the day, and lock them outside. Then lock the new birds in the coop/run, feed along the fence line. This lets the new birds explore without being chased for their lives. To find the hideouts, the feed stations, get some territorial rights.
Let the original girls in as close to dark as you dare. There may be a dust up or two, but the urge to roost will be strong. Get down there early the next morning.
If you have one or two mean ones, pull them out for a day or two.
Usually this will work pretty easily, if you truly have enough space and hideouts. The fact that the birds you are adding are a wee bit older will help. They should be laying soon, so that makes them slightly higher in the pecking order, but in a strange place, knocks that down.
Mrs K