You can update your billing info within QuickBooks Online.
Let me show you how:
From the Gear icon, select Account and Settings.
Click the Billing & Subscription tab.
Select Edit, then enter the details.
Click Confirm card when you're done.
You can take a look at this article for more details with regards to updating your billing and subscription info: Update your billing and subscription info. You'll find the steps along with related links in the article I provided.
If you have other questions, don't hesitate to post them below. I'll get back to you as soon as I can.