You can change the order of menus and links from the Menus button on the Site Toolbar at the top of the window.
First, be sure you are signed into your site. As an administrator you will have the Site Toolbar at the top of your window. Click Menus to work with your menus and page links.
Menus have page links associated with them and are listed here in table form. Click the up or down arrows next to the menu or page link you want to move. The item will shift up or down in relation to other items. Click Finish when you are done.
Changes to your site are immediate.