It's Very simple and easy but most peeps just imagine how and besidesMost people usually think about it thatYou can Only do that with PcBut well andriod apps makes things easier and more fun to useRight at Your Finger Tips

Let's begin
* Download Itag pro.apk* install and Launch itag* Look for the music yhu want to replace the album art cover
* You can click Album for easier search
* Select The music which you want to replace the album cover picture

* You can click Album for easier search
* Select The music which you want to replace the album cover picture
* Click Pick Picture And Insert any picture of your choice as yhu can see below then click saveveryvery easy


source : http://www.techsparkhub.com/2016/02/how-to-change-music-album-art-cover.html