The new hatchlings' text reads something like 'If you control (Dragon) attach (color)hatchling and all of it's duplicates to (Dragon) as duplicates.'

Does this effect work from hand? In other words, if I draw a shadow white hatchling and have viserion in play, can I put the hatchling on it as a duplicate?

No you cannot. In order for the cards text to go off, it must already be in play.

You cannot attach it directly as a dupe because it doesnt have the same name as viserion.

You will have to put it into shadows first, then once it comes into play, it pretty much immediately attaches to viserion.