Are you on an ipad? or a computer? If on the computer dashboard it is at the top left, right under your name. 

If on an ipad, select the button (3 bars) on lower left of your screen, then Settings, scroll to very bottom for the sign out button. On an Android phone, the button (3 bars) is on the upper left, then Settings, scroll to bottom, etc

I don't know what it is like on any other unit