Once a credit has been charged to your easyname account, you can use it to buy new domains and hosting products or to extend existing products. Should there be too little credit for the automated renewal of your products, you will be notified by a reminder e-mail.
You can always recharge credits to your easyname account by navigating to [Account] → [Recharge Credits] in your Control Panel. First, enter the amount you want to recharge your account with and then choose your preferred payment method.