As you add new pages and posts to your WordPress site, how they get added to your site’s menu varies depending on your theme. In some cases, new pages are added to your menu but in a random order. In others, new pages aren’t added to your menu at all. And no matter what theme you’re using, posts don’t get added to your menu.
To add and/or reorganize links in your site menu, you need to go to your Menus options, which are available in the Appearance section of your dashboard. Check out the WordPress Menu User Guide for full instructions.
Note that you can add external links to your WordPress site’s menu in its Custom Links section. This will allow you to link to a USM website (like the library), Blackboard, third-party resources (like the Purdue OWL), etc. You can also create a separate menu of external links and display it in a widget in the sidebar or footer of your website.