You can connect your ShipStation account to QuickBooks Online by following the steps ShipStation provides in this article.
Retailers will send orders to Logicbroker. Logicbroker then sends these orders to ShipStation, where you can ship them as normal.
When you are ready to create invoices, you can go to your QuickBooks Online integration page in ShipStation and enter a date range to send shipped orders into QuickBooks Online.
To ensure your documents are pulled correctly into the Logicbroker system, please set up your ShipStation-QuickBooks integration using Invoices rather than Sales Receipts.