When the game starts, the tile you will place next will be displayed in the bottom right corner. Clicking on one of the open spaces (hexagons) on the board will place that piece. When a piece is placed, it will be added together with the pieces directly surrounding it (highlighted in yellow). If those pieces add up to a whole number (1, 2, 3, etc.), then they will all be destroyed.
Your score is displayed in the top left corner, and will increase when pieces are destroyed.
Destroy as many pieces as you can before filling the board!