Hi, Lindyloo
Welcome to the TAS forums.
When we introduce new hens, we corn the two lots of hens together, with the new birds enclosed in their run. We do this for a week or more - thsi gets them used to seeing each other. Then at night, one they've all gone to bed, we move the new hens in with the old ones - the idea being that when they come down in the morning, they think they're all one flock. I know hens ain't bright but I'm sure they know there are new hens! Ideally, you should move both lots into accommodation new to both groups - this destabilises the existing flocks - but we don't have the set up to do this. Ours free range, so any bird being bullied just legs it but we've never had any problems (touch wood) with bullying, although there's always a bit of a ruck as the pecking order is re-established.
Hope this helps!