Here's how to use Coupon Codes when shopping in McDonalds: add new products to the McDonalds shopping cart and click the checkout. Log in or create a new account to McDonalds by entering details, then click Continue to pay. Below the listed items, you will see a box that says Add Coupon, choose the McDonalds Coupon Codes you are going to use and then the website will automatically return to the checkout page. Now you will see your actual total payment at mcdonalds.com.au.