Hi Alok,
Please read the NCo_30_ProgrammingGuide.pdf , section RFC Server programming and check the StepByStepServer.cs examples attached to the NCo zip file.
In SM59 the program Id is what the sofware developer defined in the ServerConfiguration section in the application conifugration file.
The registartion happens via calling the RfcServerManager.GetServer() function. On ABAP side the function call is as usual, no difference.