To start a new game, click on the "New Game" option at the bottom of the main screen.
Upon entering, you will find the different game modes that Word Crack offers. Once you select the one you want to play, you will see, at the top, the option to select the language of the new game. Pay attention when doing this, since once the game has started, it can no longer be modified.
At the top of the screen, below the language, you will see a search bar to find your new opponent.
Keep in mind that the opponents can be friends or random, so if you don't select your opponent, one will be assigned to you randomly.