By default, WordPress navigation menus are built automatically. Menu items (i.e. links to pages) are ordered by the date and time of page creation – newer pages are listed before older pages.
Following are instructions on how to manually create navigation menus.
Instructions
Click APPEARANCE -> MENUS in the left column of the admin area.
Create a new menu. Name the menu (e.g. “Main Menu”). The menu name will not display anywhere on the website. Click Save Menu.
Drag and drop existing pages and/or posts to the new menu. Add links to other website pages by using Custom Links located below the page and post listings.
Arrange menu items by dragging and dropping.
Click Save Menu.