how do chooks mix

It might be an idea to keep them in a seprate run next to your girls for a bit so they can see each other but not fight.

But it all depends on your birds, learning the hard way I now quarentine new birds for at least a week before letting them anywhere near mine.
Once that's done I just pop the new one's in the coop at night then next day let them out.
This is where the amount of room you have comes into play. Mine free range so they just go about their normal stuff after a little skuffle over food and eventually over time they start to mingle.

If your hens are in a run I would prob go with the seprate run idea

Don't know if I've helped or confused you more :?  

Sarah