How to download music to my ipod from Music?

Perhaps this article will help:

If your computer doesn't recognize your iPhone, iPad, or iPod - Apple Support

Plug in your Ipod to your Mac. Open Music. You should see your Ipod listed in the column on the left if it is properly connected. Look at the top right of the Music window and you will see Synch Settings. Click that button. It will open a Finder window. Select the various genres (eg. Music, Movies, TV Shows, Podcasts, etc) that you would like to Synch. Then select the specific items that you would like to Synch. Once you are done, hit the Synch button in that window. Unfortunately, if you use Albums by selecting specific albums, you will find it very frustrating, because someone at Apple decided not to also list the associated Artist. Thus you will have know way of knowing which "Greatest Hits" as an example is by which artist.