Hi joe10950,
You'll have to know how your bank sends the downloaded transaction in QuickBooks Online (QBO). You'll want to connect on the main account if the transactions download into one account. Otherwise, connect the subaccount if transactions download to an individual account.
To give you a complete overview of connecting accounts, please go to this article for more information: About Bank or Credit Card Subaccount Setup.
For future reference, you can match bank transactions in QBO: Match and categorize bank Transactions in QuickBooks Online.
Please let me know if you have further questions. I'll always be around to help you.
