hello divya

I hope you are doing good . As per your query, I would like to tell you that for getting admissions in NITs you have to give jee main exam and you jee main rank should be 10000 for getting into good nits. For getting admissions into IITS ,after appearing in jee mains you have to give jee  advance and combined score will be considering for cut off . Start preparing a proper road map as you have enough time, refer books like RD sharma , Prdaeep for chemistry, SL arora for physics and solve exemploary sections of these books

Hope you found this answer helpful. Good luck for your future