CBSE 12th

You have following options to become Aeronautical / Aerospace Engineer:
(a) B.Tech in Aeronautical Engineering after +2 stage in PCM . You may refer to following link for list of engineering colleges offering Aeronautical Engineering : https://www.shiksha.com/top-aeronautical-engineering-colleges-in-india-rankingpage-49-2-0-0-0
(b) Aeronautical Engineering is an interdiscipinary degree. You can do M.Tech in Aeronautical Engineering after B.Tech in Mechanical or Electronics & other branches.
(c) You can join Aeronautical Society of India(AeSI). The AeSI is a professional body, devoted to advancement of aeronautical sciences and engineering in India. The AeSI conducts Associate Membership Examination twice a year. In which applicant has to clear minimum 10 level of Section-A and 10 level of Section- B with training, Internship & projects of this examination which is recognized by the Ministry of Education, at par with a Bachelors Degree(B.Tech) in Aerospace Engineering of University from India.
You are advised to appear for JEE and private engineering colleges entrance examinations to to seek admission in B.Tech Aeronautical/ Aerospace Engineering.