Hi Krishna
You do not tell us your nationality. It is a given that for most NASA jobs "at the sharp end" go to US citizens. A very few go to citizens of their close allies.
So, if you meet the nationality requirements, the second thing you need is education. First degrees in physics, engineering or a related discipline are pretty much a given (unless you want a job sweeping floors). A strong and demonstrable grasp of English (without the mistakes, for instance that you made in your question).
Ex-members of the US military are also favoured.
NASA have an extensive web page, and a fairly large chunk of it is devoted to career opportunities.
http://nasajobs.nasa.gov/jobs/occupations.htm
Best of luck.