Hi,
usually the sign out icon is found in area highlighted:
Link Removed
You'll notice I'm using Chrome, perhaps, if your using IE10 you need to press the compatibility tab in the address bar? It looks like a rectangle with a slash going through it diagonally.
It might also interest you to know that you can have your email directed to the mail app in the Modern UI screen or Metro. If this is something that might interest you then please let us know and we can set you on the right path.