If you're using the Ritual app, tap on the "More" tab and then tap on "Promo code". Here you should be able to enter your promo code. If you see the"Expired" label, please let us know the code you're trying to use, we're happy to add it to your account for you.
If you're using web order via order.ritual.co, click on "My Account", which can be found to the left of the search bar. Then click "Sign-up Code" from the list on the left of the screen. If the field says "Expired", please let us know the code you're trying to use, we'll be happy to add it to your account!