A few instructions if you're lost :
To select a file, or one of the functions on the bottom of the screen,
it's the mouse wheel you have to click (Or the middle button, or both
left and right at the same time if you don't have this button).
(Or use the corresponding "F"unction button for the buttons in the
bottom of the screen. )
The left button is for "back" and the right one for "next" when you
select an option or number. They also can be used on the bottom of the
screen.
A bit complicated but you get used to it.