Static Page for non-registered members to log in

I have a site at https://www.pafr.org that is a members only site for a retailers association. I use the Members Only plug in to direct users who are to logged in to a specific page that I created in php (register.php). It prompts them to either log in, in which case they are directed to wp-login.php page, or to Register, in which case they are directed to a second page that I created in php (register-form.php).
Since these two pages were not created within the WP framework, I had to copy the style.css to the root directory, link directly to the header image, and basically recode the header and footer – which will all be out of synch when I make a change in the theme.
So finally to my question, how do I create these pages within WP so I can use get_header(); etc. but not have them appear on the navigation menu bar – which happens when I use the Page -> New option in the admin panel.