I'll pretty much echo what the others say, great advice! I also will just catch one and sit on the ground and hold it firmly in my arms. Make sure to hold down the wings and press firmly on the back. Pretty much all my birds will calm down in about a minute, and after awhile they will just sit there. And that's with some of my most flighty birds. Idk why they do that but it does seem like a chicken will calm pretty fast if their wings are held firmly against them. But you may get flapped in the face a couple of times before you get the technique right

again treat often and just sitting in the coop will soon have them used to you- I have sat out there for hours before. I also have my special call for scraps and treats and they come running-it hilarious

good luck!