brushes? installing assets, I must be missing something...

Hi Community,

I'm new, so please forgive me. I've looked at the directions I could find with Google. They aren't working for me. 95% of the brush downloads from the Adobe Stock page do not load the way it is suggested they should. 

I put them in a folder, use the brushes panel to locate them, and...nothing happens. It opens a blank brush panel, or, even stranger, a second iteration of the standard brush panel. 

Many of the brushes open as .ai files. I don't know how to turn those into brushes. They are just vector images to me. I can't get them to "become" a brush.

Usually, when I encounter this level of error, it means I am doing something terribly wrong. I just don't know how all the gurus I have googled could be misleading me.

Just as a for-instance, I've attached the opened brush menu for brush #AdobeStock_674332908. It is also the .ai file open on the artboard. How do I get the brushes on the artboard into the brush menu? There are only standard brushes in there.