Admissions into the M.Tech. programme happens only once a year (for the July Session). Advertisement generally comes out immediately after GATE result announcement and Counselling happens sometime in May-June.
Eligibility criteria can be found here.
Regular candidates are admitted based on their GATE score in CS.
Non-Regular candidates have to appear for written-test and Interview. Syllabus for the same can be found here.
More information about the Programme and Course Structure can be found here.