If you have a store credit with us, all you need to do is log in to your account to use it! As long as you are logged into your account while checking out, the credit should automatically come off your next order total.
To see the credit amount linked to your account, go to the Orders tab on your Account page. If you have a credit, you will see a message that states:
"You have $_____ of store credit. To use it, simply place your order and you will be able to choose store credit as the payment method when it comes time to pay for your order."