I thought it was supposed to show up in a nav bar. Maybe not. How would I make it though?
The reason why the about page is showing without a theme is because you selected the
page layout, which doesn’t exist in your
_layouts directory. And the reason why there is no link to the about page in your header on your main page is because you don’t have a link to it in
_layouts/default.html, specifically somewhere in here.
I hope that helps!