Hi Dharmendr,
Thanks for your kind help. Actually i got to know that NUnit Organisation itself has removed the TestRunner window(GUI) from the lastest version of NUnit. They are planning to release it with the latest version with some good upgrade.
So, In order to use TestRunner window(GUI) we should use older version <3.0 .
link:- http://www.nunit.org/index.php?p=download
Step process is:-
1. Find the download link which has GUI Runner
2. Reference it to the Project
3. Write your c# TestMethod ClassLibrary code. Buid it.
4.Open the GUI Window from start of your computer and add the TestFile -> Now run.