Yes it is completely safe to store your credit card information. All the personal account information, including your credit card information, is completely secure.
You have the option to store your credit card information when setting up your account for the first time. If you choose not to store your credit card information this option will not be available again and you will be forced to enter your credit card information each time you place an order. All information entered, including your credit card information, is secure.
See image below for more information about storing your credit card information