Select the corresponding offer of the voucher and click "Add to Basket". YOu can also shop for other items you want.
When you're done shoppping, click the basket icon found at the top right corner of the page and click "Checkout".
On "Your Basket" you will see "Enter Promo Code" on which you need to click to reveal the box labelled as "Enter promotion code here". Simply type in or paste your voucher code in the box and click "Apply". Your order total will then be adjusted accordingly.
Click "Checkout" and enter your postcode on the pop up window to check your address if it's available for delivery.
Choose your delivery option and click "Checkout".
Finalize your delivery details and payment method.