How do I change my credit card details in my apple id account?

Your Apple ID

1. Forgot iCloud Password

2. Forgot Apple ID

3. Apple ID - Apple Support

4. Manage your Apple ID primary, rescue, alternate, and notification email addresses - Apple Support

5. If your Apple ID has been locked - Apple Support

6. About your Apple ID email addresses - Apple Support

How do I change credit card details on my apple I'd account

Hello Claire

Do not go to your Apple ID to change credit card details. You must use your iPhone5S to change details.

Go to Settings => iTunes & App Store => touch your Apple ID => View Apple ID => Signin to iTunes Store with your password

=> Press Credit Card => Change your details here

Best of luck.