I can provide you with some rough info about it.The application needs to be submitted at
Govt. of India,WPC Wing,COP Section,Department of Telecom,
619,Sanchar Bhawan,
20, Ashoka Road, New Delhi-110001.
You can find the application form for conversion of your foreign FRTOL in dis link
Examination
Just go down the list and click on
New guidelines for conversion of Foreign FRTOLs.
I hope this helps.
Note:- There might be some change in rules now as this process was done by a friend of mine last year.