Open system preferences- in the dock. Then look at that window- for me it is in the third row down, all the way left. Double click that and it opens...then once you set it up, it does its stuff.
I am not aware of a way to keep it in the dock. It seems to live in system pref's.
I hope this helped!
Hey there "kkhaled ikbal", if what your stats say are current, you are running Snow Leopard (10.6.8) on your MacBook Pro.
iCloud minimum system requirements are Lion (10.7.2), which is why you would not be able to see the iCloud icon.
However, if you were to upgrade to Lion (10.7.2), then as "crampy" said previously, it would show up in your System Preferences (3rd row down, 1st in line).