First, that’s so cool that you have one! You’ll need to first need to go to harrys.com/redeem and enter your coupon code. Once you do so, you should see those items that the code is valid for pop up into your cart -- please note that the order total will be $0.00.
If for any reason this process does not work, try adding those same items (that the coupon code is valid for) to your cart, proceed through checkout, and click the “Apply Coupon Code” link on the Payment Details screen. Entering in your code will then apply the discount.
Your coupon code is good to go for 90 days (unless otherwise noted) after it was first generated.