When purchasing a job posting credit pack, those credits are placed as a balance in your account and can be used anytime with 365 days from the point of purchase.
To view your credit balance, simply log into your career center account and, from the My Account page, scroll to the bottom where you will find your balance of Credits/Subscriptions:
To utilize those credits, simply scroll to the top of the page and click on Post A Job. This will take you over to a page that has all of the pricing options at the very top and the entire job posting form towards the bottom. You will notice that some of the product options will contain red font that states PAYABLE BY CREDIT. Those are the products that you can select and will be discounted with your credit option.
Simply select one of those options and your amount will be discounted as necessary. Keep in mind credits can only be used for the specified posting products and cannot be used to add upgrades (upgrades can still be added at an additional cost).
To see these steps in action, please check out this short video: