Adding in header info

That completely depends on the theme you are using. Most times this would certainly require editing the code in the header.php file. Are you at all familiar with code? Also which theme are you using?

Yes this definitely would require editing the header.php file.
Specifically under the closing </div> of the #bs-example-navbar-collapse-1 <div> is where you’d need to enter your custom text. It would also require a bit of styling afterwards.