I believe you go to the Dashboard and then Sitemap. Changes here should recurse into the other pages. Of course, I've just started with C5, so I could be wrong! ;-)

What are you trying to add? Another page to the navigation or something else?

If it is just a page then make sure you are on the home page, click add page, select the page type and fill out the details. Then (the important part) exit edit mode and click publish my edits. You will then see the page appear in the navigation.

Adding to the top navigation and editing the existing words, like Home, About, Examples (change that to else), Contact ect.

The main navigation is an autonav block, that block automatically picks up pages that are added to the site. I believe by default the main navigation is an Autonav that's set to display pages that are at the top level only.

So, if you want to add an element to the navigation, all you have to do is add a new page to the site by following these steps:

- Go to the home page, click "Add Page"
- Select the page type, give it a name etc..
- (you'll be on the new page at this point) click exit edit mode
- approve my edits

The new page will be picked up & displayed by the autonav.