You can use your Zestful card both in-store and online on any of the products within the Zestful catalog that your allowance/rewards allow.
Check out your balances when you log in to see where and how much you have to spend:
Zestful cards will decline if you attempt to make a purchase 1) at a location that is not in the catalog, 2) at a location that is not allowed based on your balances, or 3) because the purchase exceeds the amount on your card.
When you explore the catalog as an employee (non-admin), you will only see products that you have the ability to spend a balance on. You will not see ALL of the products that exist in the Zestful catalog, rather only the ones your admin has allowed for you. Your catalog make look different (when you log in) than the catalog on the Zestful.com home page.