Search for the right faculty that performs research in your field of interest. Make sure to read through their current research, what their graduate students are researching, and publications. You can do this through various department websites or directly searching the professor's name.
Send an email that introduces yourself, explains what your interest/goals are, and how you would benefit from and be a suitable addition within their lab.
If you don’t get a immediate response, don’t worry. Faculty are busy people. Send a polite follow-up email after a week. Also it might help to email one of the graduate students.
If they don’t have openings, thank them for their time and keep looking.
Best of luck in your search!
If interested in Dr. Theodore Garland Lab feel free to browse the following webpages:
https://sites.google.com/ucr.edu/hrmice/home
https://biology.ucr.edu/people/faculty/Garland/Undergraduate_Research_Caveats.html