What I have to do get into ms in computer science in the USA as I hold a 3-year bachelor's degree?

For a long time, most US universities did not consider a regular three-year bachelor's degree in any subject appropriate for graduate study. Students who have completed or are pursuing a two-year master's degree after completing a three-year bachelor's degree in India are usually welcome. In other words, any foreign candidate or student interested in pursuing a Master's degree in the United States must have a college or university degree equivalent to a four-year American bachelor's degree. In this regard, many prestigious universities in the United States have recently demonstrated remarkable versatility. These universities already accept students with at least 15 years of study. Having said that, an increasing number of universities have banded together and are pursuing the goal of becoming the universities in the United States that accept 3-year degrees. Some universities only accept the full 16 years (12+4) of study for some post-graduate programs. Students are encouraged to contact admissions committees at all universities where they are interested. If your chosen university or post-graduate degree does not meet the 16-year requirement, you still have a few options for getting to your dream location. Non-profit organizations such as WES, which evaluates foreign students' credentials for research and higher education in the United States and Canada, can conduct an assessment for you. However, WES considers certain Indian 3-year undergraduate degrees to be equivalent to a 4-year undergraduate degree in the United States if and only if the following conditions are met: 

Division 1 of the university system awards the degrees.
The university that offers the undergraduate degree has been accredited by India's National Assessment and Accreditation Council with an 'A' or higher (NAAC).
Here is a comprehensive list of universities in the United States that accept three-year degrees, along with their respective QS rankings:

Massachusetts Institute of Technology
Columbia University
Carnegie Mellon University
University of Virginia
Johns Hopkins University
Northwestern University
Stony Brook University
Tuck School of Business at Dartmouth College
If you have any further questions just ask me.