Currently the WM Screeners app (WBTVD) interface is only available in English.  We also do not currently support subtitles.  We have talked about adding localization to the interface as well as support for subtitles but neither of these features are currently in the backlog for development.  

If you are interested in requesting additional languages please submit a ticket for a "Feature Request". Your feedback will be shared with our product development team. 

Thanks!