The Application Process

iam currently pursuing my btech from DTU(formely delhi college of engineering). iam in 2nd year(3rd semester) and my stream is polymer engineering .i have scrutinized my stream and made a conclusion that i will never become a polymer engineer. i want to study abroad and the only option left to me is gmat . Plz give me suggestion on how to pursue with the gmat preparation?which ngo to be joined?which certification to be achieved?how can one join an ngo? iam a beginner . plzz help