To integrate your Walmart account with QuickBooks Online (QBO), you'll need to use a third-party connector app, as QuickBooks does not offer a direct Link Account button for Walmart as it does for bank accounts.
To find a suitable third-party app, visit the QuickBooks App Center, where you can select one that meets your business needs.
For additional assistance in setting up your books, I recommend checking out this resource: Get started with QuickBooks Online.
If you have any concerns, feel free to reply here at any time.