Getting Manage Family to show...

I am using Mac Air with software 10.9.5. I've set up accounts for my children on my iPhone. However, when I am trying to add another member, or manage existing accounts, I cannot.

I go to apple>system preferences>iCloud per instructions (Set up Family Sharing - Apple Support) but there is no button for Family Sharing. Instead I see an "Account Details" and "Sign Out" button

How to I accomplish managing Family Sharing on the mac air?

Thank you in advance