Library Management calibre

I'm trying to sort my books in calibre. I've read the "managing subgroups of books, for example "genre" ", but I'm just not getting it.
I'd like to start with Fiction/Nonfiction, sub-divide from there. (similar to Dewey system, not as detailed)
I guess I'm not understanding some basic facts. I see that I use the tags to identify the individual books, and that books can have the same tags, but I don't get how to actually DO it in the tag browser.
When I open it up, there is a 1, and the letters.. I thought the letters would be authors or titles, but in A, I have 3 entries, only 1 A name. (file attached)
I don't know what to do the tag #1- I thought I could attach a name to it, but I haven't figured out how to, if that's the case.


Thank you for all help !

pam

Attached Thumbnails