Says you have to have an FFL or C&R to order. Is there a way around that if I have neither? Can I supply my FFL's certification and address? Doesn't appear that it's set up in a way that I could enter both our addresses.
In your case, you don't enter your address. You enter the name and address of your FFL. You pay for the rifle and it is shipped to your FFL, generally after your FFL sends a copy of their license to Widener's. Your FFL handles it as a transfer, with associated fees. Coordinate this with your FFL before you order. You might have to call in the order to Widener's if their online ordering system cannot handle it gracefully.