Please make sure you are ordering from this page: (the discount can not be applied to in app purchases)

Where it says 'Have a promo code?' enter your code and Apply. You should see a green message saying your code was applied. Close that window and continue the checkout process.

If you see a RED ERROR message, that means you code has already been applied. Click Continue.

After entering the code, the "Pay Now" price is reduced by $5.00 from $24.99 to $19.99 for HD or $34.99 to $29.99 for 4K