Having a credit on file with 500px is safe and convenient. We use the industry leading service, Stripe, to keep you data safe. You can read more about it here. Having a credit card on file gives you convenience and worry-free automatic renewals for your 500px membership.
Start by going to your Payments Setting page. Now click 'Add a Credit Card' and enter your credit card details. Be sure to click Add Card at the bottom of this page so your changes are saved.