There are two basic ways to rotate an image:
1.Click to rotate 90 degrees.
The single-click rotate basically turns your photo on one side or another. You can click the rotate left or rotate right buttons on the bottom photo bar, choose the options under the photo menu, or type ⌘+[ or ⌘+].
You can also use the menu commands (there are no keyboard shortcuts) to flip the photo horizontally (making it a mirror image) or vertically (turning it upside down).
2. Work with the Crop function’s free rotate capability.
After clicking the Crop icon, you may adjust the angle slider control to, in effect, freely rotate the photo, albeit within the constraints of the crop.