From the game:
"The object of the game is to form as many poker hands as possible by placing cards as they are called in the spaces in the bottom of the board (a 5x5 grid). Hands are read horizontally, vertically and diagonally. The maximum number of hands is therefore twelve, but total score will vary according to the skill of player in placing the cards."
Every player has a deck of cards. There is one caller, who shuffles their deck, then draws 25 cards, one at a time, and calls it out. All players then take their copy of that card and everyone, on their own board, places the card somewhere on the 5x5 grid. Once everyone's grid is filled, whoever has the highest total score, calculated based on the poker hands created when placing cards in the grid, is the winner.