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What I am looking for is an easy way to find the cover of a song TO DOWNLOAD it and then add it the the .mp3 file...
That is mainly what I use the skin that I suggested for. I let the skin start the google search for the album or artist, then I select "images" at the top of the returned page. This shows me multiple images that I can then right-click on and download whichever one I want to my computer. I then use MP3tag (there are many other apps that can be used) to embed the downloaded image file in the mp3 file I want it in.
MP3tag can also play the music file, search for and show you various images that you can select from to embed, which I suppose is the easiest and fastest thing to do. But I like to use WACUP to play my music files and the steps I outlined above are easy enough for me to do while listening to my music.
For variety, I often use different images for songs from the same album to keep from having multiple files with the same image.