In order to get an internship in IIIT Hyderabad, contact the concerned professor through an email. Attach your CV in the mail. Make sure to keep your mail to the point. Refrain from sending the same general email to all the professors in the department. Your email should reflect that you know about your area of interest and how it will match with the interest of the concerned professor.
The IIIT Hyderabad professors get a large number of internship applications. Therefore, they may not mail you back incase of a rejection. If you get selected, well and good. If you receive no reply, simply move on, don’t keep waiting endlessly. The end of third year is the ideal time for internships.
If you live near Hyderabad, drop by at the annual R&D showcase to understand what all is going on. You can have discussions with the research students on topics that you find interesting. If convinced, you can try and meet the faculty as well.
Thus, you can get an internship in IIIT Hyderabad by following the steps mentioned in this answer.