The best way to integrate new chicks with adult chickens is to brood the chicks alongside the adults so the adults accept them as flock members from the beginning. Consider that when planning your next batch of baby chicks.
So, now you need to play catch-up by getting the chicks out with the adult hens in a safe enclosure so they will be safe from attack during the introduction phase.
The best and quickest way to do this is by putting up a temporary "panic room" where you have small chick-size openings that are too small for the adults. Keep the openings closed for a week during the introduction phase, then open them, allowing the chicks access to the run or outside. The chicks can duck back inside whenever the going gets rough, and food and water left inside for the chicks can't be taken over by the big chickens.
For pictures of this set-up in my run go down to the second link under "Articles" and read the one on outdoor brooding.