If Want to join and study in NITs  all over India first after finishing your 10th class you have to finish your intermediate in in MPC curriculum under any of the state boards in India.

After you finish your intermediate you have to prepare throughly for the JEE mains exam conducted by the national testing agency.

Then you have to attempt the JEE mains exam and you need to qualify in that exam to secure a seat in any of the NIT as you opted for computer science engineering you should score a good percentile in the JEE mains to get a computer science engineering seat in the NIT s.