Hey there!

The first things first, you will have to build an excellent CV enclosing all of your curricular and co-curricular activities.

Then write down a moving statement of purpose. And ask three referees to write down a recommendation letter for you.

Appear for the GRE exam and also the TOEFL. Make sure, your marks are excellent.

Then, apply for the Harvard University and mention that you are an international student and hence would need a scholarship too. Also, you may apply to additional external scholarship for Indian students/international students that are provided exclusively for Harvard.

Hope this helps. Good luck!