After 12th, you do a course in mechanical engineering, you will have to clear engineering entrance exams like JEE MAINS, BITSAT, VIT, SRM, and more. After you clear exam you can admission in top engineering colleges.

Here are top engineering colleges listed.

You have the time to appear for Jee main and other engineering exams therfore keep your preparation focused.

Follow a time table and stay focused on it.

Make your concepts strong as you have enough time you can dedicate it to wven the toughest sections.

Go through previous year papers and even appear for mocks.

Once you clear the exam and complete the btech course, you can simply appear for Mtech course or PSU jobs through GATE. 

This is the pathway you will be required to go through.

Good Luck.