Contact a PI to inquire about joining their research lab. Although most PIs would appreciate it if you came in for office hours, most students utilize email. In your email include: major, year, future goals and research interests; relevant coursework; why you are interested in joining their lab; and your general availability (10-20 hour commitment per week is typical).
Step 5. Research!
Students receive units for participating in research. Depending upon the department, your PI may provide you authorization codes for enrollment (as occurs in PharmSci), or you may need to fill out some forms to receive authorization codes (as typically occurs in BioSci).