How do I update the credit card or find invoices?

If you're an account owner, head to Adminland and click the Handle billing & invoices link under Account Owners:

Screenshot of the Adminland page with an arrow pointing at the "Handle billing & invoices" option available to the account owners

NOTE: You need to be an owner to make billing changes and see invoices. Not sure who that is? Head to Adminland to see who owns your account.