Doesn't support my music files?

This is probably a really stupid question, but I can't figure out how to use this program. It says the only files that it supports are m3u, m3u8, and cue. I can't load in any music or playlists at all because it's all in mp3 format. I cannot see any other import option.

I also can't add any directories because when I click on the relevant directory location it just says "no files match your search" and nothing shows up from the entire drive.

Once again this is probably a really silly thing, I'm not usually a Windows user and all I wanted to do was change the artist name on an album I've got because for some reason Windows won't let me edit any music details at all despite all my fancy admin privileges etc, like it's not even an option, simply nothing happens when I try to click on the values. This is why y'all need jesus Linux.

Seems like a massive hassle to change one single name but c'est la vie.

Oh yeah, and I've got version 2.76 on win7.

Thank you in advance for helping me sort out my relentless stupidity

You want the "Add directory" option, not the "Import." To add individual files you need to right-click on them in Windows Explorer and use the context menu which also works on directories.. There is also an option to load subdirectories under Options/Directories. Were you looking at the "Load Playlist/Cuesheet"option under the File menu? There used to be an option to do that from the context menu, but it disappeared somewhere along the line. I put it back with a registry entry if you're interested.

Just an addition:
You can also D&D single files from the Windows Explorer (or iTunes) into MP3tag.
And if you press the Ctr-button while D&D-ing the file is added to the already loaded ones.