Here's a little step-by-step how to:
1.- Go to Honey to download and install the extension.
2.- Go to godaddy and pick your domain/domains and go to the checkout page like you normally would
3.- If you installed the extension correctly, you should see that orange button at the buttom that says "find savings", click it and the magic will be done.
4.- Wait until it test all the coupon codes and gives you the best one
5.- Buy it
I'm not affiliated with the extension developers and I copied most of the instructions over from the SEO forum. Just want to make my first post here a helpful one.