If you’ve received a promo code for a ClearVPN subscription, you can use it on your profile page by clicking the Redeem a code line next to Account details on our web page - https://my.clearvpn.com/
Please note that the code provides you with a subscription for a month(s) which is independent of the subscription you can purchase on our website or Play/App Stores. This means that promo code can’t extend a subscription if you’ve already purchased one.