When you save Album art in track Open its properties -> Album Art -> Save for all track in Album -> Ok

EDIT: But I like the Idea

I've imported many songs into MM and am in the process of adding Album Art.

When I select a song w/no album art .. I right click and select "Auto-Tag from Web .." .. and usually find the album for my song.

I would like to have that album art automatically added to all of the songs of the same album in my Library (rather than selecting each track of the library).

Is that possible? If not, what is a good alternative?

-bob