The Navigation Bar links below the banner are a great way to highlight important pages of your site - e.g. categories, biography, and contact pages. You can include links in the Navigation Bar to other pages of your site, including your blog's categories, or an outside website.
This article describes how to link to category index pages in the Navigation Bar and how to create a new page and link the page in the Navigation Bar.
Add Category Index Link To Navigation Bar
Each category on the blog has an index page which can be linked in the Navigation Bar. Before a category index page will be created, a published post needs to be assigned to the category.
To get the category index URL, go to the Archives index for your blog. You can click the Archives link on your blog or add archives.html to the end of your blog's address. All category indexes will be linked in the Archives. Click on the category name to go to the index. Then, copy the category URL from the browser address bar.
To add the category to the Navigation Bar, go to Design > Content for your blog. Click the pencil icon 
next to the Navigation Bar module. Enter the category name and index page URL and click Save Changes to update your blog.
Create New Page To Link In Navigation Bar
You can create an unlimited number of pages to supplement your blog. A contact page can be added which includes a contact form. A page about the purpose of your blog can be created and linked in the Navigation Bar.
First, you can create a new page by opening the Compose button drop-down menu and selecting New Page. A page is created similar to a post using the Rich Text editor. After publishing the page, click the View Page link to open the page in a new window or tab.
Copy the page URL from the browser address bar. Then, similar to adding a link to a category index, go to Design > Content for your blog. Click the pencil icon next to the Navigation Bar module. Enter the page name and URL and click Save Changes to update your blog.
Repeat the steps for the number of page or category links you wish to add to the Navigation Bar.