1. To play with two players, click Challenge, then Multiplayer.

 

2. Create a new account or just choose Guest Login.

 

3. Both players should choose the same play area.

 

4. Once in the play area, one player should invite the other to a game. 

 

Note - Guest players will get a randomly generated name, so it may be difficult to find each other if you don't create an account with a recognizable name.