Creating a budget is offered and available in the QBO Plus and Advanced versions, bruce18.
The list of available features based on the level of plan in this link: https://quickbooks.intuit.com/pricing/.
If you're using Simple Start or Essentials, you can follow the steps in this article on how to upgrade your subscription: Upgrade your QuickBooks Online subscription.
Then, follow the steps here to create a budget: Create and import budgets into QuickBooks Online.
Keep me posted if you need more help when creating your budgets. We'll make sure that you get the help that you need.