The instructions just assume that 'powdered' is what most people can get, because that's what most herbal sellers, sell.
You can use fresh, dried, or powdered - it will still be better than anything you can buy. But if you're going to use dried and you have a choice between dried whole or already powdered, get the dried whole and macerate them once you've started tincturing them.
You don't have to dry them - but I think drying them makes them hotter.