What is the machine and what OS you are currently using? iCloud is available in Lion 10.7.2 upwards and Mountain Lion. It is also available in IOS5, I believe.
It's always particularly helpful when your profile is filled out (and up to date). Ideally you should mention your product or computer model, the model identifier and the OS you are running. To find that detail go to … Apple menu > About this Mac > (plus) More Info. A rough guide to your location can often help too. Anyone trying to help you would be greatly encouraged to see this.