Get the artwork for an individual CD by right-clicking on one song (off the CD) in your list. As the right-click function opens a list of options, scroll down to "Get Album Artwork." The album art will then be added for the entire CD with that title.
Find the artwork for all of your albums at once by clicking "Advanced > Get Album Artwork" from the iTunes navigation toolbar. In the top viewing window, you will see the message "Processing Album Artwork" and a running tab of the albums that are being processed. This does not take very much time. Sometimes you will receive a message that states the artwork could not be found for specific albums.
Locate artwork for albums that are not in the iTunes database at the Album Art website. This site is a vast repository of artwork for CD covers and DVD covers. Type your album into the search field. When you find the matching artwork, add it to your iTunes library by right-clicking on a song (from that CD) and scrolling up to Get Info. From the options, choose "Artwork." Simply drag and drop the album picture from the Album Art site into the open window on your iTunes. Click "OK." Watch the artwork pop up in the Cover Flow View.
To add album art when you find the CD cover on another site (such as the group's website or the artist's label), save the picture to your desktop. Then in iTunes, right-click a song from that CD, scroll to "Get Info." Choose the "Artwork" tab. Click "Add," pull up the saved picture from your desktop and then click "OK."