Unfortunately (from my experience) MetaBrowser is unable to change the metadata.
I have added .wtv as the type of file to look up metadata for and it just doesn't seem to work. If I change the file from .wtv to .dvr-ms it sorts/renames the data but doesn't apply the metadata.
The only way to do this (that I'm aware of) is to convert all your files from .wtv to .dvr-ms. You can use dvrmstoolbox but you can also create a batch file which can do it (my preferred method). I hope I'm wrong about this but I know that MediaBrowser has a hard time with thumbnails and metadata with .wtv files and they just don't mesh well.
I also think that the creators of MediaBrowser don't have a .wtv fix on there priority list. In fact when I heard that they were going to start charging for MediaBrowser my first thought was that they would have to fix this problem for me to get my wallet out.
Again if I'm wrong about this please tell me and point me in the right direction.
-Chris