Find the track that you want to assign a picture to in iTunes or Windows Media Player. Left click on the track to highlight it, then right click and select "Get Info" or select the "Advanced Tag Editor" in Windows Media Player.
Select the tab for "Artwork" or "Pictures" from the new window.
Click the "Add" button and find the desired JPEG photo that you want to assign to the track from your computer.
Add the picture to the music by clicking "OK" or "Open" to add the picture as album artwork, and then close the window.
Play the track and view the newly assigned picture.
Download free MP3 tagging software such as Mp3Tag, ID3-TagIT or MusicBrainz Picard.
Run the software by clicking "File" then "Run" or double clicking on the desktop icon.
Find the track or tracks that you want to assign pictures to by typing the directory, such as "My Music" where the tracks are saved into the bottom left-hand corner.
Highlight the songs that you want to assign pictures to by left clicking on them once. Right click in the window with the round record inside it and select "Add Cover."
Select the JPEG image that you want to assign to the tracks then click "Save" to apply the changes and view the assigned artwork.