Cupid's Undie Run is a fun run, not a race, so there are no bibs or timing chips to pick up beforehand.  For most cities, check-in (where you get your wristband, red drawstring bag and earned incentives) is the morning/day of the race.  A few cities will have early packet pickup prior to the event.  If your city is having an early packet pickup, you will receive an email about it, but also check your city's Facebook event page to stay up to date.