iTunes finds artwork method:
Open iTunes
Show items with artwork
(if artwork blank)
Right click first song
Choose Get Album Artwork.
If iTunes cannot find the artwork method:
In IE, search Amazon
Click on cover
Right click drag and drop to desktop
In iTunes, right click
Get Info
Artwork tab
Drag and drop graphic from desktop
There may be an easier way, but this is what I have found to work well for me.
