Hi there,

BHU is one of the most prestigious universities in India and to answer your question the eligibility for BSC in Computer Science is that the candidate should pass  10+2 or equivalent examination with a minimum of 50% marks in the aggregate in Science subjects with Physics, Mathematics plus one of the following: Chemistry, Statistics, Geology, Computer Science, Geography, and Informatics Practices.

Now on how to go about preparing for the entrance market is flooded with books which can help you with your preparation for the same, you need to analyse the patter of the exam and the type of questions asked from previous year question papers, Arihant publications has a good guide book to help you with the preparation of the exam.