Dear Arjunvishwa,

First of all a person can not design a whole car

But if you are interested in Car designing, there are two fields

1. Car Sketching

2. Engineering Design

First you decide what you want to do.

If you want to become the first one, then you can do some course like Autodesk ALIAS, in which you can learn the sketching, clay modeling and then you can become a Automotive Sculptor.

If you want to become the second one, then you can do some CAD courses like CATIA and UG, and apply for companies who are working on these softwares.

You can join in as a Design Engineer.

I think it's helpful for you.

Best of luck