1) How can I add another administrator(s)?

On the site's main Admin page:

  • click the Account tab and
  • scroll to the Admin section, 
  • click Update to Add, Delete or make the administrator not Active.

The original administrator, the person that created the site, cannot be deactivated or deleted.

When adding an Admin, the new Admin will receive an email requesting them to click a link to have them create a password. This password will be managed by the new Admin. 
If password is forgotten, then "Forgot password?" link on the login page will create a new password.

The only difference between a super_admin and a regular_admin, is that a super_admin can see the Account tab. 
The Account tab allows the Admin to maintain additional administrators. If the Account tab is not visible, then the user is just a Regular admin.
The same Catalogs, Views, Users, Images, and Attachments will be shared by all the administrators associated with the site.