If you want to change your filing method, click on the File menu at the top and go back through the Filing screens and change to File by Mail. You may need to remove the payment method you previously choose when you were going to e-file.
[Edited 04/9/19 5:55 EST]
Did you pay with a credit card or select to have it deducted from your refund? If you have not actually filed it yet go back through the File tab slowly and read all the screens and watch what you click on.