problems starting out with subtitling app

Hi Paul

Firstly, thanks for great webinar/subtitling plugin demo. Looks like a really useful tool.

Following the Wiki instructions, clicking the 'Additional installed File Types exist' isn't possible as it doesn't show despite them being installed. 

Also, if I open a new file to translate and click on Subtitling preview the box is blank instead of being able to upload a video link...

Am I missing something?

Thanks for your help