To play Groo: The Game, start by giving each player a set of building cards and dice. Your goal is to be the first to build a large town by playing the building cards to earn victory points. Roll the dice to see if Groo the Wanderer shows up or to get resources and 'Groo heads'. Use resources to build your town and 'Groo heads' to attack other players' villages. You can also develop armies to attack other players' cities. The game should finish in under an hour. When storing the game, keep the cards in a dry place to prevent damage. And remember, have fun and enjoy the strategic battles with your friends!