Have a conversation with Professor Fig in the classroom
Read the Owl Post and Meet Professor Fig
After completing "Welcome to Hogsmeade" and returning to the Common Room, you will receive an Owl Post from Professor Fig. Read the letter to trigger "The Locket's Secret" and meet Professor Fig in the classroom.
Use Fast Travel
Using Fast Travel allows you to reach the classroom quickly. Open the map and select "Astronomy Tower" to enlarge the display. Choose "Professor Fig's Classroom" to arrive instantly.
Talking with Professor Fig in the Classroom
Once you arrive at the classroom, go up the stairs in the back and talk to Professor Fig. If Professor Fig is not there, examine the light that appears in front of the desk and choose "Wait" to pass the time.
Learn Incendio After Completing the Quest
To progress in the next main quest, "Secrets of the Restricted Section," it is necessary to learn Incendio. Advance through the task quest "Professor Hecat's Assignment 1" and side quests to learn Incendio before Professor Fig returns.