Hello student if you want to pursue B.tech Aerospace engineering then you need to appear in Jee main entrance examination to get admission into top engineering college. B.tech aerospace  is a 4year undergraduate programme for students who are willing to pursue their career in aerospace engineering.
JEE main eligibility - candidates must passed or appearing class 12 with physics chemistry and mathematics with minimum with minimum 75 percent marks aggregate from a recognized board.

Feel free to comment if you have any doubt
Good luck