To
turn the image or any part of the image, you can use four effects:
turn on 180° (accessed from the "Other" drop down
list)
turn on 90° counter-clockwise (press the appropriate
button)
turn on 90° clockwise (press the appropriate button)
turn on any angle from -90° up to 90° (choose Custom
rotate...
from the "Other" drop down menu list
In the "Custom rotate" dialogue, an Anti-aliasing flag allows
you to improve the quality of the rotated image.
The turn occurs immediately as you press on of the buttons, or as you
move the
slider on the "Custom rotate" dialog box, and you can see
its effect in the edit area and
panel of properties of the object.
Press Apply button to make your changes permanent.