how to add subpages? “parent page” not working

Hello,

I am trying to create subpages and have clicked on the appropriate parent page on my dashboard when I post, but it doesn’t seem to be working. What happens is that the title of every child-page I want to post ends up in the menu bar on the home page, written over the main page titles (so the whole thing is a mess). In other words, all the child-pages end up as parent-pages. Is there something else I should be doing?

Thanks in advance.

PS Sorry I am not sure which version of WordPress I am using…it seems to be one right before the last update (someone else built the site for me and I am now updating it) although when I clicked on update it said that it is already updated.