If your products are set to track inventory levels, those levels will be reduced as you update orders.
Follow this process once you have received an email from your payment gateway (paypal/authorize.net, etc.) that your funds have been received.
1. Login to your site and from Tienda Choose Orders
2. Find the Order you want to process and Click on it
4. Choose Payment Received in the Drop Down menu.
5. Check the box Do Completed Order Tasks. This will complete the task of reducing the inventory level.
6. Check Send an Email to the Customer
You may write comments in the box to be added to that email
7. Click Update Order. Then Click Close, top right
The system will send an email to the customer. An example follows.