Take physics, chemistry and maths with computer science after Class 10. After Class 12, you may take any or all of the various engineering entrance tests like JEE,BITSAT,VIT, SRM & etc. You need to clear a written test to get into a bachelors programme in the department of computer science and engineering (CSE) at the IITs or institutes like the National Institutes of Technology. If you cant get into an undergraduate programme in CSE in an IIT then you can try for those colleges which dont ask for any entrance tests.

Good Luck!!!