You can't! You use your bag. You can't put it in PC like you do in the other Pokemon games.
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You can't store items on Pokemon Diamond and Pearl, as your bag now can carry an unlimited supply of items.
somehow
You can't rotate items. They stay in the direction you get them in.
no where ha ha who ever you are
You cannot clone Pokemon and items on diamond and pearl and platinum, but you can in emerald!