See first of all well done for geeting nit silchar. Now in nit silchar if there is any scheme regarding fee waiver then you can apply. For fee waiver every institute has certain requirements. 

Talking about you being an obc candidates you will need to submit your obc caste certificate,  then your income certificate of your parents issued by the competent authority in your state, then they may demand income tax return of your family.

So these are some documents required. Also you will give your id proof, and other things as mentioned by your college.

All the best.

Thank you.