The Nav Bar is the area under your blog title where you can add links to pretty anything you want.
To create a page or edit an existing page go to "Pages" and select "Add New" to start a new one or "All Pages" to see existing ones. To edit an existing one scroll over the headline of the page you want to edit and select "Edit" when it appears. Make the changes and select "update."
To create a new page select "Add New" and then add the content you want, then hit publish. This will not add the page to your stream of posts. After the page is made click on "Menus" under "Appearance". All of your pages will be listed there with their headline. Check off the pages you want and click "Add to menu".
Those pages will then appear in middle under "Blog Navigation". To complete adding them select "Save Menu" on the right.
To add links to your nav bar go to the " Menus" page where it says "Custom Links". Add the link you want, give it a title and then "Add to menu" as you did above with "pages".