The technical answer to this depends on whether you are in the honors program or not. In either case, however, you should take a look at the webpages of faculty members in your department (or even in other departments!) to see whose research sounds interesting to you. Contact several professors briefly explaining who you are, when you anticipate graduating, and why you are interested in their research. Faculty may not always have space/time/money for a new student, so it's a good idea to reach out to multiple labs and to be open-minded about the research. It's also a good idea to reach out a full semester before you'd like to start. Your new faculty research advisor will know how to register you for these courses.