Hello,
Check out this link for full instructions on installing web sources and any other things into MP3Tag.
But in short, in MP3Tag itself: click File → Open configuration folder → data → sources.
In your zip file, copy TMDB#Results.inc and TMDB#Settings.settings into that sources folder. These are the inner workings of the scripts so please make sure they’re in that same folder with your .src’s and not renamed or changed in any way or else the scripts will throw that error.
In your zip file, there’s a folder called Search containing TMDB#Search - Movie.src, TMDB#Search - TV.src and TMDB#Search - Multi.src. These are basically your interface for the script that run off the other two files. Copy any or all of these three into the sources folder to try it out and see which suits your needs best.
From there, you can copy over any other .src’s to try out what they offer as you please (but they’re not essential 
).
I’m releasing a new update tonight so I’d suggest deleting your old TMDB files and trying again with this new lot 