1. The first step is to seek out the GrubHub promo code that catches your eyes on this page and hit the Get Code, found on the right side of the coupon title.
2. After clicking once, you'll see the offer code displayed and copied automatically to your clipboard.
3. Then go back to the shopping checkout page of grubhub.com, where you can find the promo code box and paste the code into it.
4. As a final step, you need to press 'Apply Code' to view the size of the discount on your current order.