<p>professors are already assigned to their courses (most of them, anyway). the only way you can “pick” a professor is by looking at who is teaching a certain course, and deciding whether you want to take that course with that prof or wait to take it a different semester with (hopefully) a different professor. sometimes, there will be multiple sections of the same course, taught by different professors, and you can try to get into the section taught by the professor you want, if the seats have not been filled up yet.</p>