Changing the Order of Pages in the Top Nav Bar

Hi,

I have a website and whenever I create a page, it adds the title of the page to the top navigation bar on the site. This is all fine (though I would like the option of having a page not appear in the topnav).

Anyway, no matter what I do, the pages appear in the topnav in alphabetical order, not necessarily in the order I would like the pages to be read or in order of importance.

Is there a way to change the order?

Thank you