Once you have added the items you wish to buy to the Basket, click on the Checkout button, you will see a summary of your order, then click Pay Now. 

Choose Voucher from the payments methods shown and you will see the screen below. All the information required can be found on your voucher. 

Pay particular attention to the date and value. The date is likely to be in the year 3000 and the value (without the £/$/€ sign) must be entered as the exact value of the voucher, not the order.

Once all the details have been filled correctly, click on the 'Add Voucher' button. An additional payment method must be used if the voucher does not meet the cost of the order. Whereas if your voucher value is higher, an email containing a new voucher (your change) will be sent once the transaction is complete.