Here's an article that shows how to set up a Live game. I don't know how up to date it is, but it's a good place to start since it's illustrated. Looks like you select Unrated from a drop down menu.
https://support.chess.com/customer/en/portal/articles/1444881-how-do-i-start-a-new-live-chess-game-
This is the only place where I've ever played chess but I go through huge periods of inactivity so I don't know all of this site's features. I just want to play live games for fun right now and not worry about rankings. How do I do that?