To apply a discount code during checkout on Smilemakers.com, customers should first ensure they have their desired items in the shopping cart. Once ready to proceed, they can navigate to the checkout page. There, customers will typically find a designated area or box labeled for promotional or discount codes. They should enter the code exactly as it appears, taking care to avoid any extra spaces or typographical errors. After entering the code, it is important to click on the appropriate button to apply the discount to the order. The system will usually update the total amount to reflect the discount if the code is valid. If any issues arise, checking the terms and conditions related to the discount code might provide clarity on its applicability and limitations. For additional assistance, customers may want to refer to the relevant section on the website for more detailed information.