How to insert album cover art on music files?

Glad to hear. 

.wav format is not designed for tagging including artwork. Using it for that is a kluge.  Expect issues. Flac files are designed for that and work well. Plus the lossless compressed data format makes managing large libraries more viable. I think everyone who starts with wav ends up either forgetting about it or switching at some point. I wish I had switched to flac sooner. Fixing tags after ripping can be very time consuming even with automated tools like Picard.

Technically, no audio degradation if done lossless at same resolution and a good quality streamer that works with flac format is used. Try it and see. There is always a chance some streamers do better with one format than another Even if source music content is identical, but should not be the case if done well. Some report differences case by case but has not been an issue for me. I have thousands of releases in my flac music library that I stream all the time and sound quality is never an issue.   Many were converted to flac from wav using dbpoweramp batch converter.  I’ve ripped exclusively Directly  to flac though in recent years

Ozzy wav format might be an issue for what you want to do. Wav format is not inherently flexible with tagging. Never tried Wav with these tools. I started with wav and used dbpoweramp to bulk convert wav to lossless flac which is very flexible with tagging.  If tagging files with art and other info for usability matters to you I would suggest converting to flac.  

Yes the dbpoweramp editor has an option to select image files you store on a directory on your computer. 
Picard might also not sure.  Never tried. 

Picard can be downloaded for free. Very powerful and able to auto tag and add album art automatically in many cases.

if you already own and rip using dbpoweramp the editor is included.  Otherwise a nominal cost to download. 

I use the music file editor that comes with dbpoweramp to Manually fix tags and art as needed.  Just right click on the files and tag and add artwork as needed. 
In most cases dbpoweramp does a good job of adding cover art at rip time.   If not then O use Picard software which is pretty good at auto tagging and adding art.  I Only use manual dbpoweramp editor as a last resort,  often when converting from vinyl where auto tagging tends to not work as well.