It really could not get more simple than this, but all too many people insist on confusing themselves on this point by listening to bad advice peddled by people who supposedly have closed this deal or that deal or 50 deals on their word.
In the body paragraph you will basically express your interest in taking admission. Important things you are going to mention include the basis for applying to the school. Why do you think this school can build up your career? List down all academic achievements and special skills that would help in making your letter stand out from rest of the applicants.