Be sure all other players have joined before you start the game. Once you select Play Yahtzee, you'll see the scoresheet and an option to Start Game.
If you're playing with others, they can join your game by using the same room name. The room name can be anything you like (ex: 'Joan's room' 1). To get started, enter a name for yourself (ex: 'yahtzee-player-100') and a room name. Yahtzee is multiplayer! You can play by yourself, or with up to seven of your friends. Each turn, you roll dice and then score one row on your scoresheet.
In Yahtzee (also known as Poker Dice, Yacht, Generala), the goal is to score more points than your opponents.