I taken the small instance from amazon EC2. I unsed the linux/unix option while purchasing the instance. Now in reserved tab that show me instance is running. I am confused how to use that reserved instance.
The reserved instance is used by the first instance (of the same size) that is running. So if you stop your small instance, you'll find the reserved instance is stopped too.
By buying a reserved instance you simply get a discount on the running costs of a single instance (of the appropriate size).