Personas that a user has is based on their enrollment and roles. The persona names are hard-coded into the system, and cannot be edited at this time.

The only way to add/remove a persona from a user, is to edit their Roles and/or enrollment.

Personas are also tied to past roles as well (for example, a user with the Past Teacher role will still have the Faculty persona).

You can read more regarding past roles and personas here.