When you take CSE Computer science and engineering course or B.Tech Computer science and engineering.

When addtional skill for to train in online or

Coaching Centre for

*C++

*C

*Python

*Java

For software engineering or B.Tech CSE you need to have Physics Chemistry and Mathematics as your ground subjects in class 12th but if you get a chance to study any programming language in school then do choose it because it will help you later. Else, if computer isn't available as an additional subject in your school then you can join any coaching center for it or take any online programming course you can start with any language like C,C++ or Java.

Hope it helps.

Thank you