I am a mech engineering graduation of batch 2016. I want to pursue a career in comp sc. How do I do it?

As you have completed your graduation in Mechanical branch. I recommend you to learn few computer languages C, Java, c+ & Python. This are current trends in Software industry. There are few institutions which teach this languages around 6 to 8 months.

From my point of view, if you want pursue your career in CSE then you should have basic knowledge of computer fundamentals and have some certification of language or some projects as to show in your resume so that people understand that you really have a interest in it.