Can't sync music to iPhone

From this article: https://support.apple.com/en-us/HT210612 the second screenshot looks nothing like what I see on my computer:

I don't see a way to import music to iTunes on my phone, and "Add file to library" and "Add folder to library" don't do anything when I try.

Why doesn't my iTunes look the same as in that article, what could I do to fix it, or do I need to do something else? Thanks!