To switch writers during a live event you first have to bring up the "Event Control" window.  This window can be opened from the "View Events" screen after you log in.  Click for the "View Events" link on the left hand side of the window find the event you are looking for and click on the "Event Control" link.  The window will look like this.



From here, click on the "Change Provider" button.  You will be presented with another window that looks like this.



Select the writer you want to take over writing for the event and click the "Change Provider" button.  This will cause the current writer to become disconnected from the event.  If the new writer is already connected to the system and is not writing for another event, they will be pulled in immediately.  If the new writer is not connected yet, then the system will wait for the new writer to connect and then will pull their connection into write for the event.  Writers can be switched as many times as necessary for a single event.