In Navigation, located under System Settings, you can change the order of the items on your websites navigation bar as well as add new items to your sites navigation bar.

To add a new Navigational item just click the Add button in the top right corner of the page. Pick the parent page and the page that you are wanting to add to the navigation bar then click on submit.

To change the order of the navigation items simply grab the + icon on the item that you wish to move and drag it to where you are wanting it to be placed.