I have got an admission to IIT Bombay for an M.Tech in Aerospace Engineering in the general category. My aim is to become an aerodynamicists but I am average in studies. What skills do I need to learn in my two years of stay over there in order to pass out as a good aerodynamics student?

Congrats on getting admitted for an M. Tech. degree in my department !
I am assuming that you have been allotted the Aerodynamics Stream.

We will try our best to enable you achieve your dream of becoming a good aerodynamicist. What you will need to do is to acquire a good background in Fluid Mechanics and Mathematics. You will be required to undergo a few compulsory (core) courses, and most of them will build on these two fundamental subjects. You will undergo a core course to improve your communications skills and competencies. You will also need to clear some Elective courses, covering topics in the area of your specialization, your discipline, and of general interest to Engineers.