I've got the steps to help upload your file into QuickBooks Online (QBO). I'm happy to share them with you.
If you're referring to the bank transactions in .QBO file format that you need to import to QuickBooks and if you have your account connected to online banking, you can start uploading the transactions by following these steps:
Log in to your QBO account.
Click on Banking at the left pane.
Go to the Banking page.
Select the blue tile for the account you want to upload the transactions into.
Click on the drop-down arrow beside Update, select File upload.
If your account isn't connected to online banking, you can click on Upload transactions under the Banking page.