Dear Promila,
There are several good MBA Institutes in India and Top rung amongst them are IIMs. To get admission in any of the good Institutes you need to sit for an Entrance Examination after which you have to clear your Group discussion and personal interviews to finally get into one of the good Institutes.
To get into IIMs you need to sit for CAT for which the eligibility is to have a degree from a recognized University with 50% and above aggregate marks. If you fulfill this eligibility you can go ahead and appear for CAT. However, as IIMs are the apex in Management Education you need to be outstanding at every front, be it academics, extracurricular or other parts of selection procedure.