If you cast a creature spell of the chosen type, Door of Destinies will get a charge counter before the creature enters the battlefield. The creature will enter the battlefield with the additional boost to its power and toughness.

Creature types, such as Human or Sliver, appear after the dash on the type line of creatures. Notably, artifact is not a creature type. A creature may have more than one creature type, such as Goblin Warrior. Such a creature would benefit from Door of Destinies if the chosen creature type was Goblin or Warrior.