For the couple dozen albums in my iTunes library for which iTunes can't find cover art (I've got most of it on my hard drive), how do I add that art to the iTunes-supplied cover art? I've tried highlighting just one song off the album and dragging the picture to the "Now Playing" box and that works for just the one song but when I highlight all the songs from that album and drag the picture to the "Now Playing" box, it doesn't get applied to all the songs. Is there a way I can make that happen or do I have to highlight/drag for each song?