how to close finder on my desktop on my computer

The Finder IS your Mac. It's what runs MacOS. It's your desktop, your folder windows and everything that has to do with displaying your content. I can understand that it's odd that Apple shows the black dot under the Finder icon as always active, but basically that's the point. Without the Finder your Mac isn't usable.

You don’t get rid of it, as it is an integral part of the Mac OS.

Get to know the Finder on your Mac - Apple Support

you can't really close the finder. You can press the red x in the corner but that just hides is. Finder is always active. Can you post a screenshot so I can see what you are seeing?

Have you tried "right" clicking on finder and hiding it?

You cannot get rid of the dot. You can hide your dock so it is out of site.