When navigating to Setting > Administrator and selecting Add a new admin there are two options available:

1. New: Create a new administrator account.
2. EMM User: Select a user from among the previously added users to be an administrator.

For case 1, enter in required fields and click Save.

For case 2 (administrator is an EMM user, who already exists and has devices assigned to him in Knox Manage), simply select the name and apply the required role for the user.

For more information, please visit: Knox Manage Admin Guide - Add an administrator