Class 11

Start learning C, C+ or java.or can start either with C or C+. There are several video lecturers available on YouTube if you are not comfortable with textbooks and it really doesn't matter that you should first join college and then start learning software languages. There are several students I know who are mastered in this field before joining college. But it really takes serious dedication with lots of frustration.
Try to practice on coding websites like HackerEarth or HackerRank then you will learn how to practically implement your codes.
Have some basic knowledge of computer Architecture, like how it works, how data or instructions flow. It's also available on YouTube.
There is not only one field to learn in software Engineering, if you are pursuing your B.Tech degree, you must have known about this, if not u will. New sectors are emerging day by day, but the concepts do not change.
Language changes like people now switching from php to django.
So you should learn at least 9-10 languages (doesn't matter if u are mastered or not) but you must master at least one language, and that's the key to be a programmer and hence Software Engineer.
It's all about programming and coding.