Messages Clicking a name in your Address Book will open their AV window and add a "named" button to your chat window.

Switch to messaging a different person by clicking their button in the Chat window

To contact a user without adding them to your address book, press the "messages" button to display your incoming/outgoing call and message log. Enter their address at the + and hit Return

The Chat window bar can hold 8 buttons maximum, after that when you open a new window it will drop off the least used one to make room.