Use the Cancel Entry button (in My Entries section of the app)
Upon final submission of any paid contest you cannot edit your picks. However, any entry can be cancelled as long as you cancel within 10 minutes of the moment you create your contest and it is more than 15 minutes before the start of the first game. If both conditions are satisfied, you will be fully refunded. You can cancel your entry in the My Entries section of the app by finding your entry and clicking on the Cancel Entry button.