how to instal icloud on my mac - I still have Mobileme and Icloud does not appear

The minimum requirement for iCloud is Lion 10.7.5 (Mavericks preferred): the iCloud Preference Pane does not appear on earlier systems - the MobileMe pane appears on Lion and earlier but is now non-functional - you cannot now open or access a MobileMe account.

To make use of iCloud you will have to upgrade your Mac to Lion or Mavericks, provided it meets the requirements.

The requirements for Lion are:

• Mac computer with an Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
• 2GB of memory
• OS X v10.6.6 or later (v10.6.8 recommended)
• 7GB of available space

Lion is available in the Online Apple Store ($19.99). Mountain Lion (10.8.x) is also available there at the same price (though it's reported to have been removed from sale in some countries so may well cease to be available generally) but there seems little point as the system requirements are the same for Mavericks (10.9.x) - which is free - unless you need to run specific software which will run on Mountain Lion only.

The requirements for Mountain Lion and Mavericks are:

• OS X v10.6.8 or later
• 2GB of memory
• 8GB of available space

and the supported models are:

• iMac (Mid 2007 or newer)
• MacBook (Late 2008 Aluminum, or Early 2009 or newer)
• MacBook Pro (Mid/Late 2007 or newer)
• Xserve (Early 2009)
• MacBook Air (Late 2008 or newer)
• Mac mini (Early 2009 or newer)
• Mac Pro (Early 2008 or newer)

It is available from the Mac App Store (in Applications).

You should be aware that PPC programs (such as AppleWorks) will not run on Lion or above; and some other applications may not be compatible - there is a useful compatibility checklist at http://roaringapps.com/apps:table