Under Configure tab > Language, you can choose the language of the interface labels and translate the course content into multiple languages using XLIFF export and import.
Here you can choose the language of the interface or add your custom translation.
In the All-in-One template, currently Afrikaans, Arabic, Bulgarian, Croatian, Czech, Chinese (Simplified), Chinese (Traditional), Danish, Dutch, English, Finnish, French, German, Greek, Hebrew, Hungarian, Indonesian, Italian, Japanese, Kinyarwanda, Latvian, Lithuanian, Malaysian, Norwegian (Bokmål), Norwegian (Nynorsk), Polish, Portuguese, Romanian, Russian, Slovakian, Slovenian, Spanish, Swedish, Thai, Turkish, Ukrainian and Vietnamese are available. More languages will be added soon.
All text items of the template interface (button texts, titles, headings, field names, error messages, validation messages, etc.) can be also translated into any other language.
To add your custom translation, in the language drop-down select Custom. Then, in the drop-down near the Custom translation field, select the language you would like to customize.
NOTE: Easily change the language of the authoring application under My Account settings. The supported languages are English, Dutch, German, French, Spanish, Portuguese (BR), Mandarin (simplified), Ukrainian, and Italian.