Page Slugs and Permalinks Questions

I am setting up a new web site using WordPress as CMS at https://www.ohiocichlid.com. That links takes me to an error message ‘page not found’. I can navigate from there to ‘Ohio Cichlid Association (https://www.ohiocichlid.com/?page_id=3, top item in navbar). I want to make that my main page (index page/home). How do I do that? On my old site (www.fmueller.com) I believe I simple made the page slug of the main page ‘home’, but I can’t see how to define the page slug in the latest version of WordPress.

I am also having trouble with using pretty permalinks on https://www.ohiocichlid.com. In https://www.fmueller.com I chose under Options/Permalinks/Custom structure: /http:/example.com/category/post-name/

I tried the same for https://www.ohiocichlid.com under Settings/Permalinks, but if I do so none of the pages are found if I click on the navbar. What am I doing wrong? (I am pretty sure the server has Apache’s mod_rewrite module, but I have emailed the web host to double check).

Finally, unlike https://www.fmueller.com, https://www.ohiocichlid.com doesn’t seem to have an .htaccess file. What’s up with that?

Many thanks in advance!

Frank