Hello there, john-cato-comcas. I'll share insights on how you can achieve your goal today.
If you're referring to importing your QuickBooks Desktop company file into QuickBooks Online, you can use this article for the step-by-step process: Move your QuickBooks Desktop file to QuickBooks Online.
If you're referring to importing your company file from a different software into QuickBooks Online, I suggest looking for a third-party importer tool that can integrate with QuickBooks. To be guided on what app to use, you can go to the Apps menu in your QBO account and browse for an app that suits your business needs.

I look forward to your reply. And ensure to assist you further if you have additional concerns.