If you have been granted a subsidy, sponsorship, or promotional discount, you will likely be given a discount code that you must use to redeem it.
In order to do so, register as usual, and when you reach your cart, click "Proceed to Checkout":
From there, click "Add a gift certificate or promotional code":
Enter your code in the box and click "Add Code":
Then click "Proceed to Payment" and make sure to pay the balance in full. If you need to pay in cash at camp, please see this article.
Your discount has now been applied!