During the events of the main quest, you will return to the Abbey/Monastery where your character lived.
In the back is a church building with a tower/steeple. When you walk inside, you will immediately be given a quest to go grab the bottle of perfume that is on top of a building just to the west along the lakes shore.
You can either swim to it or walk through the woods/road. It is very close by. Simply jump up onto the roof, get the bottle, and return to the church building.
The achievement will unlock and you will gain a permanent bonus to your characters personality stat in game.