navigation bar should be already available with almost all themes of MyBB.
is it missing for you ? which theme you are using & what is your forum url ?
or do you mean highlighting of prefix for a thread in the navigation bar ?
The above images seem that you want default MyBB navigation. That's pretty easy, you can revert the navigation templates and you would get the same navigation. (Make sure you have a backup of those templates).
Better that you provide website URL and theme name to get a better understanding.
try adding <navigation>
at the bottom of header template of your theme
^ if you have <br />
before <navigation> then remove it and add it after <navigation>