Get them to know you. If possible, it might be a good idea to actually visit the university that interests you the most. You'll have an opportunity to meet some of the faculty and students, to see their physical facilities and to talk. Rank your schools. Apply to more than one program.
Every university has a different procedure.
Sometimes different academic departments in the same university have different procedures. The best way to learn the specific process is to contact the graduate coordinator of the academic department in which you're interested. This is usually a faculty member who can be reached by calling the department's main office. Again, different universities have different requirements. Could be free.