To translate subtitles, Khan Academy translators use amara.org. This allows you to take the existing English-language captions, and translate the text into your language. You'll have to sign in to Amara and contact your Language Advocate, to be granted access to Khan Academy Team Workspace, and be assigned video subtitles to translate. For more information, you can follow the directions here to get started. Subtitles will be published and sent to YouTube after your team reviews them.