Click Create Room.
Select number of players for the game.
Once you create the room, check out the room ID at the top. In the example below, the room ID is 64959. Tell your friends to Join Room with the ID.
You can click the settings button at the top right and customize the rules. See Wikipedia for more details about each option.
Once the room is full, you can click the Start button at the bottom right to start the game.
Here's the objective of the game:
Get rid of all the cards one has as fast as possible by playing progressively stronger cards than those of the previous player. (Wikipedia)
Card Rank is:
3 < 4 < 5 < ... < 10 < J < Q < K < 1 < 2 < Joker
3 is the weakest and Joker is the strongest card.
Enjoy the game!