The price listed on the website is $399.99. The discount is a 20% coupon code that will be applied at the payment information screen. Note that it only works on regular priced items.
Add the item to the cart. Sign in or checkout as a guest. When you get to the payment screen, before you enter any payment info, scroll to the bottom of the screen where it says More Ways to Pay.
Click on Enter Promotional Code
Your cart price should drop 20%. YMMV.
Note that Breville is normally excluded so the coupon code may work on other excluded items.