I need some advice on adding new hens to an existing flock?

[CrayCrayChick]

Hi, I am a beginner in raising birds, so I'm not so sure. I raised 12 chicks from day one and now they are just a little over 6 months. All of my girls are free-range, and their coop is not massive but it's cozy (they're out free-ranging for the whole day anyway).
I wanted to add a couple of hens to my flock, but I know it's a tricky business! I heard that chickens are territorial, too. My girls are all really sweet and love people, so my question is if I add 2 hens to the flock, will my existing flock hurt them? What if the hens that I add to the flock are a year-old? Would that make the situation better?
Or should I just forget about it? xD Thanks to all who answer!

 

[CrayCrayChick]

Also, do certain breeds specifically clash? My hens are red sex links and white leghorns.

 

[WalkingOnSunshine]

Go slow. Put the new girls somewhere the flock can see them and interact, but not peck. A pen next to an existing pen is good. Keep them separate but where they can get to know each other for a week or so. Then put them in the coop at night, so they all wake up together. Be prepared for the newcomers to be chased and pecked for a bit.

They chickens don't care much about each others' breeds, but they might separate according to color a bit.

 

[CrayCrayChick]

Thank you!