If you have coupon code for a discount you can use it in one of the next steps:
1. On cart page
Open cart page and find the “Coupon code” field. Enter code here and click on “Apply coupon” button.
2. On checkout page
On checkout page find on the top find the message ‘Have a coupon? Click here to enter your code” and click on this link. Then enter code and click on “Apply coupon” button