Adding a box at the top

I am trying to get my site set up. I want to add some labels (pages?) to the top bar (now have “Home” and “Sample Page.” I want to add a label for “About” with sub-pages for “About me” and “About the blog”.

I added a page “About Me” but it does not appear on the top where “Sample Page” does.

How do I do this?

Thanks