How to change forums member "type"

I notice that in the minibb.com forums, user "Paul" has the title "CEO" under his posts, while registered users have "Registered User" and guests have "Guest." How can I assign a specific text strings to a specific user or users?

As the Administrator, I would like to create one or more "categories" or "titles" and then manually assign users to one of theses. Does this make sense, and is it possible?

Thanks for any help.

Custom Rankings? minibb_solution_customranks.zip
See here

It's not about the "Custom Rankings" add-on. It's a built-in miniBB feature: Custom member titles. Here are some advanced modifications of the setting.

Thanks!