Full width nav

If you want people to be able to help you, please include as much information as possible and, in particular, link to your site.

Sorry. My work in progress wordpress website is https://www.kalree.com

I would like to stretch the menu to the full width of my website. So far, I am only able to either get it to float left, right, or have it centered.

I’ve worked with html before, but never worked with php. I would assumed in html, I would need to add the <span> to stretch out the width of the nav.