Hi Bishnudutta. Not much that I can add to what Joanne has already provided except to say, be sure to pay special attention to the NSCA requirements for certification because each certifying agency is different in what they require in order to sit for their certification exam. Good luck!
In addition to information about the NSCA exam and or certification, I strongly advise the purchase of practice exams and or the text book “Essentials of Strength and Conditioning” found at https://www.nsca-cc.org/online_store/products.html?steps=cl&ci=1. Both were extremely helpful in my preparation.