At the end of your round you map move armies from any one of your territories to any other of your territories, provided that they are connected directly, or by an unbroken chain of connected territories. Select the pair the same way as before, and move using the same gestures as deploying or fortifying - except that tapping and holding a territory after moving some armies to the other resets to their pre-reinforced state.
Then tap [End turn] to end your turn.