In QuickBooks Online(QBO) US, it's not possible to import journal entries. However, I've got two options to help you out.
First, you can manually create a journal entry. Here's how:
Go to + New. It's located at the top left corner of your screen.
Underthe Other tab, look for Journal Entry and click it.
Choose an account in the Account field. Enter the right amount in Debit or Credit. If you're not sure, you can check with your accountant for guidance.
Depending on where you entered the amount, either in the Debit or Credit field, enter the same amount in the opposite column.
Enter information in the memo section so you know why you made the journal entry.
Click Saveand new or Save and close.
Another option is to utilize the third-party app to import the journal entries into QBO.
If you would like to see a demonstration of how to use a third party import utility like Axis Online to import your journal entry files in batch into QuickBooks Online then I have made a recording here on YouTube.