Setting the default page

I’ve never had this problem before, and I’m probably only having it NOW because the site isn’t originally mine, but I’m having problems setting the default page for a site:

https://www.steamrollercopies.com

This lead to the problem in my previous post. I set the URL to https://www.steamrollercopies.com/home to try and get it to go to the right page… and screwed up the entire site. ?? Anyway, there has to be some way to designate a page as the “home” page… doesn’t there? ?? Or if not, how do I get rid of that annoying “page not found” message? What page is it trying to find? ?? Heh, I know, a bunch of really stupid questions, and I’d never have this problem on a site I built myself. *blush*