Hi cristio22,
I am not sure if I have understood exactly what you require.
The number of places is determined by the particular Betfair market. So if Betfair have only offered a 2 place market, then you can't bet on it as though it was a 3 place market.
If you are asking about betting on a horse to finish in one specific position, then I don't think it is possible on Betfair, such as only 2nd or 3rd.
You could potentially do something similar using 2 bets. For example, if you want to win money only if a horse finishes 2nd or 3rd, but not 1st, then you could BACK the horse in the place market (for example to win money if it finishes 1st, 2nd or 3rd) and also submit a separate bet to LAY the horse in the win market to ensure that you don't win anything if the horse finishes 1st.
However perhaps you are asking about how to submit an EACH WAY bet? If so, then you need to select the each way market (usually available on UK races). Click this link for more info about
each way bets on BetfairKind regards,
Gavin