thanks you bsd-keith,
now i want to start xfce4 desktop !
i have do :
1/ pkg_add -iv xfce4
2/ pkg_add -iv slim slim-themes
3/ Create a file called " .xinitrc" and add the following line into it. (not sure in the good place)
But the window manager loaded is FVWM !
How to start Xfce4 Desktop ?