If it fully cured,you can put it right in the tank.Smell it...it should smell fresh.Cured or uncured can be added to new tanks that doesn't have fish,coral, and inverts...never add uncured rock to an establish tank,uncured needs to be cycled in a separate container.
If it has hair algae or other nuisance algae,I would scrub as much off as possible.(an clean old toothbrush works fine)