To speak with the king and his court to discuss the findings. It is only accessible after clearing the investigation that he had asked the party to do.
It is only required to explore the dungeons he assigned you to, finishing the side dungeon isn't needed to progress with the next events. However, the side quests, additional dungeons and occasional travelers met with the journey give insight toward the plot, so it is recommended to finish it.
To access "Arrange Meeting", go to the Ishmag Castle.