Can't setup / configure Super Administrator

I’ve installed WP 4.4.2 onto Centos 6.7 via epel. It’s all working fine except I couldn’t understand why Add Plugins wasn’t showing up even though my user is set to Administrator.

Now, after reading a bit, I understand there is a Super Administrator (or Network Administrator) role that I need to setup in order to see the Add Plugins menu. When I try to access /wp-admin/network or /wp-admin/plugin-install.php I get a message that says:

“You do not have sufficient permissions to access this page.”

I have looked at my permissions in the database using phpMyAdmin and it looks like my user has the right permissions (according to posts made on various forums).

There doesn’t seem to be any documentation explaining how to configure a Super Administrator. Any help would be welcomed.