Icloud storage
How do I manage my storage payments on Icloud?
MacBook Air, OS X Server, Yosemite 10.10.1
Verify or update your payment information by following these instructions: Change or remove your Apple ID payment information - Apple Support
One method it describes is to log in with your Apple ID here: https://appleid.apple.com/. Click the Edit button in the Payment section.
Also, read iCloud storage upgrades and downgrades - Apple Support