If you're a new customer:
At the last step of checkout, click on 'Have a gift or promo code?'. Enter your promo or referral code in the field and click “Apply” to add it to your order. If the code is valid, you'll see the updated price reflected immediately.
If you're resubscribing:
On our homepage, below the top photo, there's a promo field you can enter the code into and click APPLY. If the code is valid, the promotion will automatically be added to your account and you'll be successfully resubscribed! (Welcome back.)