First, select Las Vegas Event 4(you may have to complete earlier tournaments to unlock this). After choosing, begin the tournament.
Try to only play hands that you have a shot at winning (use the different screens that come up when you hit "RT" in order to help with your decision to fold or stay). Every time you win a big hand, hit "start." This will save your progress. If you ever lose a big hand, quit to the dashboard and reload your last save. Continue until you are the only one remaining in the tournament and you receive you achievement.