How to apply for NASA after Btech,from ECE?

ECE wasn't really the best engineering stream you selected if you wish to go for NASA. Aeronautical engineering or aerospace would've been far better, and you would've got many contacts through the course to get into NASA.

Now that you have taken ECE, the only way is to try contacting the people pursuing aerospace, or the teachers of aerospace, and forge contacts into space research laboratories in India firstly. After that, through contacts only, you might get a chance to apply for NASA.

Hello,

For getting job in NASA you have apply for it. You have to built a strong resume and send it to them. Then they will recruit you. But you have basic knowledge on science, technology, engineering and mathematics (STEM).

All the best.