Use the keyboard A, W, D, S or arrow keys Left, Up, Right, Down, and mouse button - if the game description "Triple Mahjong 2" is not stated otherwise.
Triple Mahjong 2
Description: Combine in this game 3 (instead of 2) of the same tiles to remove those tiles. You can only select free tiles. Free tiles are highlighted. You can combine a flower tile with any other flower tile, the same applies to the season tiles.