There are two ways to add people to a chat room. Promote a Chat or add them. It depends on the chat room and what the owner wants. So, check out the guidelines of the room or ask the room owner.
1) Add to a Chat room
PC
MAC
Click on the button, find the person you want to add in your list. Add them. They will show up in the chatroom. Everybody will see you added them. Now, send a little message into the room, like welcoming the new person so the room pops open for them.
2) Promote a Chat
This will produce a very long link. Send it to someone by email or Skype to invite them to your room (or to a room you belong to).
If you send a link to someone you might want to let the room know (or the owner/hosts) that you invited someone, best give them their Skype ID name, so they can greet them and know they are coming from you and not from out of cyberspace.
You are welcome to send them to this page so they learn how to book mark, close and leave a room.