You need to keep in mind that the internships at top B schools such as IIMs/ISB/XLRI will be strictly literary and not industrial. If you are interested in such things or your college does not have any strict criteria of doing only industrial internships, then you can definitely apply at these institutes.
Whenever you want to do an internship, start applying at least a month before the start of the internship. During the summers many professors are out of India or are on vacations or are attending some seminars, so apply as early as possible.
The process of application is as follows.
You may even get a stipend which such internships.