How do you add album art in iTunes 12? everything I've tried doesn't work

Question

how do you add album art in iTunes 12?

Answer 1

Two methods:
Right-click on the album, select Get Album Artwork.  iTunes will determine whether this album is available from the iTunes Store and, if so, download the artwork image from the Store and associate it with the media files.
Right-click on the album, select Get Info and then the Artwork tab,  Then:
click the Add Artwork button, navigate to and select an image file on your computer, or
drag and drop an image file from your computer to the Artwork tab, or
copy an image to the clipboard (for example, from a web page) go to the Artwork tab and press Ctrl-V (there's a bug in iTunes 12.0.1.26 such that right-click > paste does not work here
For the second method, you can also access the "old style" editor window from iTunes 11 by holding down Shift as you right-click > Get Info.
Lastly, there are three cases in which you can follow these procedures but artwork is not correctly associated with or embedded in your media files:
your media are in a format that doesn't accommodate embedded artwork - typically WAV files.  To embed artwork you'll need to convert to another format - Apple Lossless or AIFF if you want to preserve lossless quality, AAC or MP3 otherwise.
your media files are read only - to fix this, use Windows Explorer to find the folder that contains your files, right-click and select Properties.  On the General tab there's a check box labeled "Read-only" - if this is checked, or is grey (sometimes blue), click the box so that the flag is unchecked and the box is white.  Click OK, and then OK again when the "Apply changes to this folder, subfolders and files" option selected.  Now try adding the artwork again.
Windows permissions issues are preventing iTunes from updating your media files (there's some anecdotal evidence of a change in this behavior in iTunes 12).  See turingtest2's notes on Repair security permissions for iTunes for Windows for advice on fixing this, then try adding the artwork again.