If you need to update your payment information, you can do so by:
Hovering over your profile image in the top right corner of the navigation bar
From the dropdown menu, you'll see ‘Personal settings'
From there, you will see an option 'Subscriptions & billing'
Clicking that link takes you to your Subscriptions & billing page, where you can modify or update your account details.
If you have any trouble, just raise a ticket with us via the Help & Support messenger on the site, and we'll help you out.