You're then added to the queue of working operators. Please wait before a client is assigned to you. The time to wait largely depends on the traffic volume of your website and the number of your working operators.
To leave from the queue of working operators, just navigate to any other pages or close the browser.
Status of chat button
Livemoz is designed in such a manner that the chat button is shown to clients automatically when there are any operator available and hidden otherwise. You don't need to turn on/off the button manually.