Hey,
M.Sc in Computer science is a two year programme.
Here is the list of some of the colleges in Mumbai that offer Masters of Science in Computer Science:
1.St.Xavier's College
2.SIES College of Arts Science and Commerce
3.Mithibai College of Arts,Chauhan Institute of Science
4.University of Mumbai
5.S.K. Somaiya College of Arts Science and Commerce
See,the basic eligibility criteria is that a candidate must have passed graduation in B.Sc Honours Computer Science or B.Sc Applied Physical Sciences with Mathematics and Computer Science. Candidates who have completed B.Sc (General)  with Mathematics and Computer Science are also eligible to apply.
Admission to the course is through both Entrance test and Merit. It varies for different Institutes.
Hope this helps.
Good luck.