How to create admin user accounts?

From the top level dashboard of the Game Manager (click the PlayFab logo in the upper left corner), click "Users and Roles" for the Studio in question. Next, click "Settings" for the user to be modified. On the Details tab for the user, any Studio Admin can make the user a Studio Admin by clicking "Make user an admin on this studio" and then clicking Save User. And any Title Admin can give the user Title Admin rights by clicking on the Roles tab in the user's settings, then clicking Assign roles on the title, selecting Admin, and then clicking Assign Roles.