Letter of Explanation for canada study permit visa

I am going to do canada study visa process for Master of information Systems Security Management. So that i need well explanation letter like Statement of purpose. Currently I am studying Master of Information Technology Management, I was in final semester so I completed Information system security, Cyber law Security and information System infrastructure courses from MSITM. But I realized that's not enough with my program, i want to learn something more about Information systems security, that's the reason again I am going to do Master of Information System Security Management at Concordia university of edmonton, Canada. So Please provide me a well explanation letter.