Yes, you can file RTI application for Railway Recruitment Board Kolkata. Railway Recruitment Control Board is a government organisation in India. It was set up in 1998 in the Ministry of Railways (Railway Board), New Delhi. It manages the appointment of new employees to work in Indian railways. There are 21 boards situated in different parts of India and RRB Kolkata is one of the boards under the Ministry of Railways. It comes under the Jurisdiction of Eastern Railway.
Hence, it is a public authority under section 2 (h) and is obliged to provide information under section 2 (f) and 6(1) of the RTI Act, 2005. The RTI application must be made to the designated PIO of the Board. The application needs to be made on the online portal https://rti.gov.in/
For further assistance in filing RTI application to central government or RRB please refer https://onlinerti.com/how-to-file-rti-online-for-center