Many times, I do not give step-by-step instructions. I would rather teach you how to figure this out on your own than to just give you the answer. This is the old proverb that goes something like "it is better to teach a man to fish and feed him for a lifetime than to give a man a fish and feed him for a day." So in that vein, I will point you to the Oracle documentation which contains your answer. This way, you will not only get a resolution to your problem, but you'll learn where to find these answers as well.
Take a look at the Backup and Recovery Advanced User's Guide. Pay attention to Part III, "Using RMAN For Database Transport, Duplication and Migration." RMAN is the tool to duplicate a database on another platform.
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