In e-commerce and online shopping a coupon code, or promo code, is a computer-generated code, consisting of letters or numbers that consumers can enter into a promotional box on a site's shopping cart (or checkout page) to obtain a discount on their purchase.
When you have a coupon code, please login to user control panel, click Account, License and choose one compatible package such as 30-day Standard package. It shows the price, for example 21.90 USD.
You will see the link: Do you have a promo code / discount code ...
Click on that and it shows a text-box for your entering the code. And then click the Apply button.
it will reduce the price, for example from 21.9 USD to 15.33 USD
Click Buy Now button to make a purchase with saving your money.