How do I assign transactions to accounts in QuickBooks?

When you import a .qbo file into QuickBooks, either desktop or online, you do through via QuickBooks Bank Feeds. Bank Feeds displays the downloaded payee name for each transaction. You need to specify the QuickBooks payee and assign an account name for transactions. Bank Feeds creates rules as you go through that process, so subsequent transactions from the same payee will default to the same account. Once most of your customers/vendors have been processed once, everything becomes automatic.