After your payment processor has been connected to eCC, all orders show be downloaded with the payment status as "Unpaid". This is setup within the orders screen of the store configuration. The orders status that is checked to be downloaded, in the "Process payments" should be set to "Yes".
The Process Payment button will be added to the actions in the inbox.
Step 1: Select unpaid orders within the inbox and click the process payment button.
Step 2: eCC Desktop will communicate with the payment processor to process the total order amount authorized.
Step 3: When the payment has been successfully captured by the payment processor, the payment status will change to Paid and the order(s) can be posted to QuickBooks.