If the transaction is downloaded in your For Review tab in the Banking screen, you can allocate them to an income account if it's a money transaction and an expense account if a money out transaction.
If you did not manually created a transaction in QuickBooks Online, you can Add the downloaded transaction to QuickBooks. If you recorded one, you will be able to Match them.
Under the For review tab in Banking page.
Find a downloaded transaction with the Add option in the Action column.
Select the transaction to expand the view.
Review the recommended Category. This is the account QuickBooks wants to categorise the transaction into. For example, for a office expense, QuickBooks may suggest categorising it under expenses related to travel. You can always change the category and put it in a different account.
Select the supplier or customer name as needed.
Review the other information and fields.
Click Add when everything looks good.
If you've recorded a transaction in QuickBooks, click on Find Match option. Review the matching records found.