You can put a shout box in your Header, your Footer or a Board Description area

To do it in your Header or Footer go to:  Admin > Manage Styles > Edit Header/Footer
To do it in a board description create a board for the shoutbox,  paste the shoutbox code in the boards description area.     Its nice to do it this way as you can limit who can see it by the boards permissions

You will need to sign up for a shoutbox/chatbox someplace and get the code:

     Here is a list of chat/shout boxes:
     
     www.cbox.ws
     www.yellbox.com
     www.myshoutbox.com
     www.shoutmix.com
     www.shoutbox.us
     www.tag-board.com
     www.tagboards.tk
     www.tagboardsite.com/