Click on your cart, then click the "Check Out" button on the bottom right of the cart page.When the checkout portal has loaded, there will be a gift card/discount code box on the right of the screen under your itemized cart (your shipping information will be on the left side.) Enter your code and click "apply." If you have a gift card amount that is smaller than your total amount, your remaining total will be shown. You can then enter your credit card information to pay for the remaining total.