If you chose the store pickup option, then fill in the details of the individual picking the order up.
Enter this information and move on to Enter Payment Methods. To use your Gift Card, you can choose that option now.
Under Payment Methods click +More
Choose the Pay With Cash option. Pay at a Walmart store within 48 hours and present your coupon in person. The item will be shipped after you pay in store. This must be done in person as you cannot enter coupons on Walmart's main website. But you can present them in person after choosing Cash as a payment option.