You can apply for admission through the CSU Mentor website or the Office of Admissions and Records (LH 111), which will provide the necessary forms. It may take considerable time to obtain your transcripts and other required documents. You should allow sufficient time for the evaluation of your application-at least two or three months, longer if transcripts from non U.S. institutions are required.
Additional information about applying for the BS in Computer Science can be found at
http://www.fullerton.edu/ecs/future/admissions/undergraduate.asp for domestic undergraduate students or
http://www.fullerton.edu/ecs/future/admissions/international.asp for international students.