Press the plus icon on the screen to open the settings menu. Your main language can be selected.

For smartphone and PC:
Press the cross icon on the right side of the ‘play screen’ and select Settings on the bottom right corner. Select your language from ‘Screen Display Language’.

For Meta Quest:
Press the menu button on the left controller to open the menu screen. Then press the settings button (gear icon) on the right side of the menu to open basic settings and select ‘Screen Display Language’.