I run Windows.
On MP3 files, I am able to right click the track and choose "Properties." I do not do this process in iTunes.
Then I choose the "Summary" tab and can make changes to Artist, Genre, etc.
To change the name of the track, you can left click it twice with a pause between the two clicks and type away. However, I have noticed that iTunes and other music programs prefer to look at the meta data that you manipulate in "Properties."
Yes. This process is tedious.
If you have a whole bunch of files to tag/change, there are programs that will do this for you for a price. I cannot offer any advice on these other than I know they exist.
Ken