Once you have clicked on the cart icon on the top right corner of your screen, review the contents of your cart and click "Checkout." Enter your code in the field marked "Discount Code" on the right side of your screen. Click "Apply" and your discount will be deducted from the total. If you're shopping on your mobile device, you will enter the coupon code on the same screen that you enter your payment method. Coupon codes cannot be combined and do not work with subscribe and save orders (auto delivery).
If your code is not working, there are several reasons why that may be the case. Are you trying to use more than one discount code? Only one discount code can be used at a time. Are you trying to use the code on a subscribe and save item (auto delivery)? Subscriptions, promotions, & bundles are not always eligible with codes since they are already discounted. Are you meeting all the requirements for the promotion? Check for minimum order value and applicable products.
Again, discounts cannot be applied to subscription orders. With Subscribe and Save (auto delivery), your order is already discounted based on your subscription level. If you would like to apply that code to a one-time order you certainly can.