The buttons are located immediately below the short help. In colour terminals, the button labels have different colours which group them by functions, usually distinguishing between processing and verification commands.
In order to ``push'' one of these buttons, you must position the mouse
on top and ``click'' with the left button. In what follows, this
operation will be called ``to click'' and will refer to the
left-hand button unless indicated otherwise. Therefore,
to exit XLong you must click the 
menu
of the menu bar and select the 
option.