Hi there mjbenard,
I see that you have some songs in iTunes and you wish to add artwork to the files. Here is an article that can help explain how to accomplish this goal:
iTunes 12 for Windows: Add artwork to songs and other items
https://support.apple.com/kb/PH20513
While your WMA associated artwork will not be preserved when converting the files for use with iTunes, you can use the information in the above article to find the files on your computer and manually add them, or you can use this step in the article to help you collect artwork for the files:
Retrieve album artwork from the iTunes Store for songs in your library: Control-click the songs and choose Get Album Artwork.
Take care, and thanks for visiting the Apple Support Communities.
-Braden