Hi Ankit,
You still need to build out an Application Model in Application Modeller. What they were describing above is merely the launch portion of dealing with the app. After launching with Start Process, you need to use an attach (navigate stage) action to connect to the application. When you use Global Send Keys, you will be able to use the root as you mentioned because now you'll be attached to the window.
You'll need to play around with how to attach. It could be as simple as attaching to the Window Title or the Process Name or a combination of both.
Respectfully,
Dave
Dave Morris, 3Ci at Southern Company