If you’d like to push your invoice to QuickBooks, click “Orders” and then “Manage Orders.” Click
the QuickBooks button, log in to your QuickBooks account, and integrate. (This may take a
minute or two.)
Follow the prompts that pop up on your screen asked you to sign in your QuickBooks. Once you are connecting with your QuickBook account then you can Export any invoices simply but clicking on "Export to QuickBooks" option.