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.
2. Creating Localization Settings
Localization settings is created automatically when package is imported. Also you can manually create via
First item in your localization settings is your default language. Default language is treated as the current language in Editor when application is not playing. Optionally, always you can set current language as your default language by calling Localization.Instance.SetDefaultLanguage() at runtime.
You can specify import location for importing CSV files into your project. Import location should be anywhere that under your Assets/ folder. The location is used for creating new localized assets from the CSV file.