They are too old to bond with the hen, and she won’t accept them. Get them full feathered (about 4 weeks) and introduce them like any other chicken. Put the brooder in coop. Week of look don’t touch. Then make a door sized so chicks can run through, but hen cannot. They will venture out and mingle. Retreating if needed. Also supply hiding spots that chicks can get away from hen further away from brooder (run, across coop, etc)
You will need multiple feeder and water stations.
@aart has a handy run down that covers it in better detail I believe