iCloud.com email address not appearing on my Mac Air

My iCloud.com email address is showing on my iPad and iPhone and I have changed the settings to send from this address but ---- the same iCloud.com email address is not showing on my Mac Air. I have followed instructions i.e. mail, preferences, composing etc but no iCloud.com address appears - just me.com. (OSX 10.7.5) Any solutions gratefully received.