The parking pass office is upstairs in the arrivals section. You have to show them your employee id, proof of insurance, and a vehicle registration and then they give you a card that gets you the rate of $3 per 24 hours. It works at any of the long term parking lots (including the garage that is attached to the terminal). The card has your license plate on it, so it is vehicle specific, but you can get a second one for I think $10.

Hope it helps.