Some cards of a given color also have special effects: Typically speaking, each turn, you can play a card that has either the same color or the same number as the top card on the discard pile. In the center, you'll see the discard pile.
Be sure all other players have joined before you start the game! They will not be able to join after you start the game.
Once you select Start Game, you'll see the cards you have in your hand. If you're playing with others, they can join your game by using the exact same room name. The room name can be anything you like (ex: 'joan's room'). To get started, enter a name for yourself (ex: 'uno-player-100') and a room name. Uno is multiplayer, and works for between 2 to 6 players. The first player to play all the cards in their hand wins the round, and scores points. In Uno, the goal is to be the first player to play all your cards.