The follow option is useful as it tells you when they run or if they are to be auctioned. The auction process is two distinct methods, there are the end of year sales, and the mid week sales, the later requires you to go to the races on the day, indicated by a little hammer top right of your main screen next to the cycle day buttons. Once in the auction itself, click the horse you want and press the start auction you may then participate in bidding.
Don't expect to many miracles, if they were any good there not likely to be sold
