Open or create your project in Unity. Then import the Asset Localization package from the Asset Store window in Unity editor. You can find detailed explanation here.
Localization settings is created automatically when package is imported. Also you can manually create via
Project Window -> GameToolkit -> Localization -> Localization Settings
You can add languages that must be available in you game as many as you want via:
or add used languages in your assets via:
If you want to use Quick Translate option, you should set Google Authentication File claimed from Google Cloud. For more information look at: