Before proceeding, please confirm which platform which platform your promo code is corresponded to. Promo codes are not valid interchangeably, with the exception of subscribed members.
iOS
Method 1：Within Grid Diary app, in the purchase interface, click on "Redeem Offer"
Method 2：Or click in the order: Me-> Help-> Redeem Offer
Enter your promo code and follow the in-app guidance
Android
Enter the purchase interface, click on "Redeem Offer"
Enter your promo code
When the offered price appears, proceed to purchase.