To do so, you should first import the translation modele file of your questionnaire. This txt file contains all the text data that have been generated for your questionnaire. You then only have to manually translate them (please mind the HTML tags that should remain as they are) and save the translated file on your hard-drive.
Then, from your web interface, you should select the interface language and the questionnaire language. Upload your file.
You questionnaire is immediately available in a new language...