I have not worked with that specific theme before. Generally, most themes will adhere the Navigation Menus to a Custom Menu. You would find this in the Appearance > Menus Tab. Usually, you would need to create a Menu from here, apply it in the "Theme Locations" option that opens up when a menu has been created. Then add and order your items, as desired.
Without creating one of these, theme can generate and order pages on its own from timestamp, unless overridden by creating and applying a Custom Menu. Nevertheless, mordecai98, the theme should provide instructions; if not, and my advice does not help guide you, then contact the theme author.
Good Luck!
