Does Mac OS X10.6.8 woks with iCloud?

Do I need to purchase and upgrade to Lion 10.7.2 from my current OS SnowLeopard v10.6.8 - in order to see iCloud under my System Preferences - still showing MobilMe?? How do I remove this and add iCloud? I thought this would be automatic when I converted to iCould......

I'm having trouble with syncing my calendar on my mac to iCloud and iPhone calendar. I just recently moved everything from mobilme to iCloud, but now my calandar wont sync correctly.

When I add an event on my iphone caledar, it will appear on iCloud but not sync to my Mac calendar.