iCloud Storage

I am Mac OS X user and tried to find out my available iCloud storage following your instruction, but when I opened iCloud icon from System Reference in Apple Menu, it says "This is not your primary iCloud account" and no available storage indicated. As I am the only user of this Mac, my account supposed to be my primary account, I believe, or I must not so familiar to what it exactly means? Could you please explain more about this message, and also let me know how can I get an information on available iCloud storage. Thanks.