To select or view a winner, go to the dashboard, head to the Giveaway you'd like to manage, click 'Select a Winner', then click the pink button to "Randomly Select a Winner". You'll then see a page with the winner's information (name and email), which you can always access from the new "Winners" tab on the dashboard.
Check out the video below to see the winner selection in action and view the email your winner will receive.