There are two types of discount codes: 

1. Automatic discounts - when we provide a discount code on the site, and you add items to your cart relevant to that offer, then the discount will automatically get applied on the checkout page. 

The offer on this example automatic discount is for the purchase of a size small Rainforest collar. When added to the cart, then the discount is automatically applied.

2. Unique discounts - if you've received a discount code from us via an email or through social media, and have added to your cart the relevant products associated with the offer, then simple enter the code in the "Discount code" field on the check out page, and click "Apply".