If a coupon code is required, click on the coupon code and it will automatically get copied. You will then be taken to the store where you can add products to your shopping cart, and then look for the Promotion Code or Coupon Code field during the checkout process. Paste the coupon code here. Click the Update or Submit button if there is one. Proceed to checkout.
Note: If you click the Shop Now button on the coupon which requires a coupon code, make sure you first copy the code by highlighting it, right-clicking, and selecting Copy. Then proceed as given above.