Per city municipal law, bicycles must possess a license (a DMV sticker affixed to your bicycle; issued for free by UCPD) in the City of Berkeley. Other nearby cities might have similar laws. Additionally, to use some secure bicycle parking areas on campus and at residence halls, campus building managers might ask that you have a license (UCPD sticker) on your bicycle.
Unfortunately the City of Berkeley does not offer bicycle licensing, but UCPD offers bicycle licensing services for free. You will need to bring your bicycle to 1 Sproul Hall between 6:30pm to 9pm, Monday-Friday, excluding holidays.
Outside of these options, you can email UCPD at email@example.com if you have questions or need to arrange a special appointment.