Hello @2020mma thanks for your question. Check out this best answer for some more info. It basically says you would go to your checkout screen, select Items > Discounts > apply reward (or code). You would enter this into the field to apply to your sale.
You can also search by customer name, and within the customer detail screen scroll down and you should see any emailed coupon offers. You cannot edit a coupon once you create it; you'll have to delete and then create a new code. I hope this helps answer your question.
