Hide menus in theme

I saw this post: https://ww.wp.xz.cn/support/topic/is-possible-to-use-it-directly-on-theme?replies=2

But do not know exactly how to implement what they were speaking on.

What I want to do is remove menus. Using the standard menu in wordpress how could I make say… the register button disappear and become say… sign out using this.

https://ww.wp.xz.cn/plugins/eyes-only-user-access-shortcode/