Dear,

In order to become a Aeronautical Engineer, you have to do these following steps after 10th class.

1. Choose science stream ( physics , chemistry , mathematics and an optional subject). This is the first step after 10th. Both 11&12th should be done with science stream.
2. Write an entrance exam ( JEE series exams ) for joining IIT , NIT. If you are joining a private institutions maybe some college will take an exam before selecting the candidate.
3. Do BTech(bachelors) in Aerospace engineering it is a 4 year long course. If your more interested in studying after BTech then take Mtech ( masters) in order to take Mtech you need to complete BTech. Mtech will be of 2 years.
4. Finally, Get a college placement.

Hope this helps!