We are using i18n-js to translate the user interface. This library provides translation facilites using the same mechanism as the Rails I18n API.
Copy the file config/locales/autotune.yml to config/locales/autotune-mylang.yml and edit as needed. Keep in mind that you need to change the 'en:' key to 'mylang:' in order to avoid overwriting other languages.
This file can be either inside Autotune or your own application. Alternatively, you can add them inside the main autotune.yml file.
To set the language within an initializer (for example a file under config/initializers/locale.rb) do:
I18n.default_locale = :mylang
Restart the application and it should work (missing keys will default to their English values).