In order to become a software engineer you can appear for entrance exam in your 12th class like JEE Main, BITSAT, SRM and Manipal

You can take CSE branch in your engineering program.

To get admission in top colleges like NITs and IITs make sure you get 75% marks in your board exam or you should be in top 20 percentile.

For more detail you can refer below link

Top Engineering exams

Good Luck!!