I was in a similar situation. I had 5 EE and 3 turned out to be cockerels I had rehome. Sooo, I went and purchased 4 more pullets (4 is the minimum), 5 weeks later. I introduced them to the run and coop at 7 weeks, separated both coop and run. We rehomed the cockerels when they were 15 weeks and started letting the 11 week olds out in the run with the 16 week old girls the next week.
This would be no big deal; they practically grow up with them. WRONG! It was horrible. My big girls chase them around back in the cage, pulled feathers and just bulling them. Thanks to the wonderful insight of the people on this forum, I ended up putting my two girls in "Chicken Jail" (4' x 3' cage in the run) for two days, to give the little ones a chance to get comfortable in the run.
The young ones would not go into the coop, too afraid of the two big girls and also, they were use to me manually putting them in every night on a separate side. I had to manually put them into the coop every night for a week through the regular chicken door, sometimes twice a night, they would run back out. I have a camera set up in the coop and run, so I could see the big girls would squawk at them, but not hurt them.
After the first week they all slept on the roost (I have one that is 7' about 2.5' off the floor). The four girls on one side the other two on the other. Last week my husband went into the run at night, and it must have scared them, I looked on the camera and all six where bunch together on one side. Tonight, there are three on one side and three on the other.....they will figure it out. LOL Queeny Coco, (attitude big girl) still pecks at them sometimes, but nothing more than pecking order top dog (chicken). I still have the cage in the run, the chickens use it as a jungle gym. lol It took about a week for them to put themselves to bed in the coop and up on the roost, but they have been doing it for the last couple of weeks. Sorry so long.

I hope it helped.