Grant system level rights to a user (System administrator)

There is a difference between System-manager and System administrator since System Manager: is a user that can manage all customers in the system but do not have access to edit system-wide settings.. Whereas System administrator: can change system wide-settings, manage all customers in the system, add/delete and alter the privileges to the other users. Note that this option should not be granted unless the user is to see everything in the system.
In the light of the above, the System administrator account has more privileges than the Administrator account.  

NOTE: Granting Administrator rights to a user does not implicitly give the rights to a user to be a System administrator since System administrator account is more powerful and has more privileges than the Administrator account so giving privileges to each must be done separately.
How to grant system level rights to a user step by step.

• Go to Administration Tab then click on the Users

• Click on the user that you want to grant the privileges to

• Click on the Additional tab.

• Check the System administrator checkbox

• Click on the Settings tab to go back to user settings

• Click on Update button and the user is a system administrator now