Big 6 Wheel is found near the entrance lobby, down 2 sets of stairs.
to Place Bet on any of the possible outcomes you choose, then
to spin the wheel. The wheel has a 1 in 54 chance of landing on Joker each time, and when it does you'll get the achievement whether you bet on Joker or not. There's no achievement need to bet more than the minimum on this particular game, so it may be wise to save your chips for achievements that do require riskier bets.