How to group chat on Facebook with multiple friends

How do I chat with more than one friend at once?
If you’re chatting with a friend and want to add more friends to the conversation:
1.Click the actions menu at the top of your chat window.
2.Select Add Friends to Chat...
3.Enter the names of the friends you want to add, then click Done.

How do I chat with a group?
To chat with members of a group, go to the group and select "Chat with Group" on the upper right side of the page.

When you’re chatting with one friend and you add more friends to the conversation, a new chat window opens for the group. Friends who are added can’t see the private conversation that you and your friend were having before you created the group chat. 

Once you’ve already set up a group chat and you add more friends, the chat continues in the same window. Friends that are new to the chat can see the full history of the group conversation. This allows them to go back and see what the group is talking about.