New chicks

first of all put your new hens into another coup and run and quarrenteen them for a couple of weeks. then gradually move the new run closer to the original run so that eventually they will be just seperated by the runs wires for a few days. Then in the evening place the new ones into the old coup when the others are asleep. In the morning you will have some fighting (this can go on for a couple of weeks) as the original hens will see the new ones as intruders in their property and the pecking order must be established. Provide several feeders and drinkers as well as somewhere for the new ones to hide.