The display tab contains the options to change where KOrn will show itself.
The first option, "Horizontal", will create a window and the contents of the window will contain the options you specified in the "View" tab (which you can get to by selecting your mailbox and clicking "Modify..."). On the other hand, selecting "Docked" will dock KOrn into the Kicker panel.
The option "Vertical" is not yet implemented.