If you've got credit in your account, you will be able to see the balance at the top of the website.
Once you have added an item to your basket, you can proceeded to checkout. After you have chosen your shipping information, you can choose to use your credit or not by ticking the 'Use credit?' box in the payment section, where you available credit should also be displayed.
This will apply the total of your credit to your order. If the credit amount covers your order, the remaining credit will still be available in your account after your order.
If the credit amount does not cover your order (as below), you can pay the remainder by card/Paypal and all unused credit will expire after 2 years.
Unfortunately, we are unable to apply part of your available credit to an order.
Click here to find out more about adding store credit to your account.