To change an existing Amazon EC2 instance into a reserved instance, first navigate to the Amazon Web Services console and go to the EC2 module. Then click on the “Instances” tab on the left and note the availability zone and instance type that your EC2 instance is using. Switch to the “Reserved Instances” tab and click the “Purchase Reserved Instances” button at the top of the page. Enter your instance’s type, platform, and availability zone in the proper fields and click “Search.” Browse through the results and select the reserved instance pricing plan that you want to use. Once you complete the payment process, your EC2 billing will shift to the reserved instance pricing.