Hi Mohan Rao,

If you want to pursue a career in the Engineering sector, then you must have to give JEE exams which are conducted by CBSE twice every year. For being eligible to sit in these exams must have your 11th and 12th passed with Physics, Chemistry and Maths. Other Subjects are your choice. After clearing your 12th boards, you may sit for JEE mains exams which are conducted twice in a year. If you qualify those, then you can sit for JEE advanced, but to be eligible to sit in JEE advanced exam is that you must have secured atleast 75% in your 12th Boards. 

I hope I was able to clear your doubts.

All the best for your Future.

And do post your queries if you have any.

Thank you