Hi Mohan,
There is no way to manually add new internet radio stations or private streams to your SoundTouch app.
The "Internet Radio" source in the SoundTouch app is provided by vTuner and uses the index from that service to display available stations.
You can search for any public station on vTuner's website here: (http://vtuner.com/setupapp/guide/asp/BrowseStations/startpage.asp)
If the station you want does not appear, you can use the "suggest a station" feature to propose a new stream they might incorporate in the future.
Thank you.