Complete Professor Flitwick's mini-quest to unlock the Charms room. Go inside and talk to him. He will call out spells that you need to cast on different objects. The following is the order he calls the Charms in:
1. Wingardium Leviosa on a bench. 2. Reducto on a statue of a bird. 3. Reparo on the pile of broken dishes. 4. Accio on a rope near the fireplace. 5. Depulso on a chair. 6. Accio on a rope near the fireplace. 7. Incendio on the plaque. 8. Reducto on a statue of a bird. 9. Reparo on the pile of broken dishes. 10. Wingardium Leviosa on a bench.