Mobile bidders submit bids via text message and do not require pre-registration. You are registered upon your first successful bid to 63485. Mobile bidders are are able to login to http://www.speedfantasybid.com/ using their username and password provided to them via text after their first bid in the same window that web bidders log in to.
Web bidders must have an account on Fantasy Bid at http://www.foxfantasybid.com/ Web bidders should login prior to the start of the game so they have the best opportunity to bid. When a car is opened, the new car will automatically show up as available for bidding.
Remember, the sooner you bid; the better the chance you'll have at winning a per-car prize.