The easiest way that I know of to delete music from iTunes is to highlight the particular song and press delete on my keyboard. If I want to delete numerous songs, than I highlight them all (you will probably have to hold down the shift/alt or ctrl/alt keys to highlight more than one). To delete an entire artist, I highlight the artist in the browser at the top of the page. If you don't have the browser at the top, just go to view and select show browser. Hope to have helped!