To change the game language on Facebook, change the language in your social media page settings.
To change the game language on hero-wars.com:
Click the globe icon in the upper-right corner of the game tab and select the desired language in the drop-down menu.
Confirm your action by clicking the Refresh & Change Language button. The game page will automatically reload.
If you cannot find the desired language in the list, it is not supported by the game yet.