You will know that your order is complete because you have clicked the COMPLETE ORDER button. You will also be taken to a page that shows your Order Number together with a note that says "Thank You" and "Your Order is Confirmed".
You will also receive an email thru the email address that you used to make the order. And if you clicked the SEND TO MESSENGER box at the bottom of the Payment Method page, you will also receive the same notification via Facebook.
If you do not get these notifications, it means your order is not complete. You need to go back to your cart and click CHECKOUT. Make sure you click all the way to the COMPLETE ORDER button.