I would have separate areas for the new ones. If they are accustomed to living together, keep them that way but if they are coming from separate pens or separate homes, have an area for each. Introductions take time and some management.
Have treats to give everyone, it is good to have a "party atmosphere" to make them feel better.
Keep the new ones close for at least a couple of weeks - they need to know where their new home is. This is less cruel than letting them wander off and get killed, injured, or hungry.
If they can see each other through fence for a while, that is about the best approach.
