artist - title want to remove artist

I see this post, but where is "function tag" ? and "file name" and where do you type %artist% - %-title% and what are you changing it to?

I'm REALLY new to this, but what I can do, I LOVE. please explain this by showing WHERE the

The "function" is the abbreviation to a menu entry. So have a look at the MP3tag window menu bar and search for "Action" or move the mouse cursor along the MP3tag toolabar just below it until the bubble help for the buttons shows "tag - filename".
After you clicked on the menu function/button a dialog window will open and there you may enter these cryptic strings with % in them.
The % shows MP3tag that it should use the contents of field called e.g. artist and not write the word artist.
Could you follow so far?