From the game’s main screen, tap the big blue play button to enter a match lobby. You can also tap the “Play” button at the upper left corner of the screen.
To get into a game quickly versus bots, tap on the “Practice” tab at the upper left, then hit the “Play” button below your Champion at the center of the screen.
To get into a game quickly versus players, tap the “Versus” button at the upper left, then hit the “Play” button below your Champion in the center of the screen. You may not be able to access Versus mode until you’ve played a few Practice matches.
You can tell which game mode you’re in by looking at the tabs at the top of the screen: “Practice,” “Versus,” “Solo Ranked,” and “Team Ranked.” Tap on a mode to switch to it, if the mode is available to you.