Where to find WordPress Tutorial for Coders???

I am used to writing all my own code, so I never had started a blog. My web host installed a WP blog on my site in 2018. I have never been able to wrap my head around how to use it. I recently figured out how to delete the author’s theme link (it said no longer supported), put my own header up, link to my site and change the copy on the sample post.

I cannot figure out how to make it so more posts can be made or people can login (if that’s a thing) to create posts.

I’ve tried to follow all the prompts when I am logged into the backend, but none of it seems to work. Every time a period or comma is changed it logs it in the php panel, but I have no idea what is needed and what is garbage so I can delete it. Any links to a tutorial that will help me understand how to do this will be greatly appreciated.

The page I need help with: [log in to see the link]