Just double-click on the icon, and slide the control to the percent of processor time you want to allow people to use. Select a person you know from the menu, and click the connect button. It's that simple. You should install the Chatter Listener fairly soon after starting Chatter. After installing, restart your Mac, so the little sucker will start working.
Some people have answering machines set on their Chatter lines.
To turn on Answering mode, use the menu selection under the Options menu.