Select the song you wish to work with and right-click it. Select “Get info” then click the tab that says “Artwork. " If the song already has an artwork attached you will see it there. If not, then press “Add” and you can then browse your entire computer to attach any image you like.
Remember that if you do not have the album artwork on file in your computer (which is almost always the case) then you will need to go and find it first and the best way to do this through the internet.