I'm not sure how to answer this, but try going down to the undercroft [where you make armor] there is a place in the very back where you can customize Skyhold and maybe choose a throne? The rest of the thrones, so far, are unlocked by judging people.
People to judge are unlocked during the course of the game - everytime one of the main perpetrators survives, they get taken prisoner. Often, when one of them escapes you can solve a mission on the war table to follow and capture them for judgement.
When someone is waiting for judgement, you can either see it by visiting the jail cells, or by simply sitting down on the throne, which becomes an object you can interact with for that reason.
The throne can only be interacted with if the game decides someone needs judgement.
So far I have found three people I could judge, as far as my memory serves me: The major of crestwood town, who drowned much of the populace of his own township as well as countless refugees to prevent the spread of the blight, one of the templar leaders who knowingly poisoned the templars under his command with red lyrium, and the chieftain of a tribe of barbarians that captured one of your patrols in the swamps after he observes a ritual to smear the blood of a goat on the walls of your castle in retaliation for the death of his son at your hands.Hope that helps.
People to judge are unlocked during the course of the game - everytime one of the main perpetrators survives, they get taken prisoner. Often, when one of them escapes you can solve a mission on the war table to follow and capture them for judgement.
When someone is waiting for judgement, you can either see it by visiting the jail cells, or by simply sitting down on the throne, which becomes an object you can interact with for that reason.
The throne can only be interacted with if the game decides someone needs judgement.
So far I have found three people I could judge, as far as my memory serves me: The major of crestwood town, who drowned much of the populace of his own township as well as countless refugees to prevent the spread of the blight, one of the templar leaders who knowingly poisoned the templars under his command with red lyrium, and the chieftain of a tribe of barbarians that captured one of your patrols in the swamps after he observes a ritual to smear the blood of a goat on the walls of your castle in retaliation for the death of his son at your hands.Hope that helps.
AndragonLea is right. You should use her/his post as solved.