Welcome to Adobe ColdFusion forums . Multiple instance is a feature of Adobe ColdFusion Enterprise. So you will not be able to achieve the same in Standard Edition.
For development purpose, install CF 10 as trial which will act as Enterprise Edition for 30 days. After 30 days, CF 10 will become Developer edition and you can continue your development.
Just to clarify a bit - running multiple instances of ColdFusion (where you have multiple independent instances running on the same physical or virtual server) is an Enterprise-only feature, as @vishu#13 said. However, running multiple independent ColdFusion applications using a single instance of ColdFusion is possible with the Standard license. Whether or not you actually need to run multiple ColdFusion instances will depend on the type of application(s) you are running and how you set up the various tiers of your application.