First, you need to figure out the position of your message box. To do so, open a playtest and, open a message window, press F12, on the CONSOLE tab, and type:
- SceneManager._scene._messageWindow.x => this will return the X coordinate.
- SceneManager._scene._messageWindow.y → This will return the Y coordinate.
Then you put the face window with Top and Left orientation, and set their offset according to the coordinates of the message window.