It's easy to update your credit card details.
1. Click on the user dropdown in the top right hand corner of your screen and then click on Account settings.
2. Then click on the 'Billing' tab (the billing page contains an overview of your plan, payment info and listed credit cards).
3. Click on the 'Update' button 'Payment details: Your cards' section.
4. Enter your new credit card details and hit 'Update'.
That's it, you're good to go.