Splitting Filename to Track and Artist?

I have tons of downloaded music, whose filenames are mostly just "artist - track name". I want to split the file name in the action window, but all I see is "FILETYPE" and "FILEOWNER". Which one from the "split by separator" would give me access to the filename of the song? Thanks in advance!

You are using the wrong action because you don't want to split a tag-field. This is for making 2 same tag-fields out of 1.
What you need is the action-type "Guess Values" or you can use the converter "Filnename -Tag" which is easier to use because it gives you an immediate preview of your format string.

Converter Filename - Tag:
Format String: %artist% - %title%

Action Guess Values:
Source Format: %_filename%
Guessing Pattern: %artist% - %title%