After redeeming your ticket at the Gwanghwamun ticket office, you can board the bus; once you've exchanged your ticket there, you're free to hop on and off throughout the day for a wonderful experience.
The bus departs from Gwanghwamun and makes a loop to 15 stops, including Myeongdong, the Blue House, Namsan, and Hanok Village.
Get off at the stop you wish to explore, enjoy your free time, and then board the next bus every 60 minutes.