This achievement is easily earned on Level 3 of the single-player mode. Simply complete the move as indicated by the tutorial arrow (slide the red gem to the left in order to complete the "T" as shown) and let the cascade happen. You should get around 12,400 points by the time it ends. Once Free Fall kicks in and starts awarding bonus points you will likely finish with over 54,000 points - enough for the unlock. If for any reason you don't get it in the first try, just replay the level until you do. It will come soon enough.