You can rotate your photos left and right (clockwise and counterclockwise) with the Rotate button on the toolbar of most views. You can also make a mirror image of any photo.

To rotate right, click on the Rotate button. To rotate left, press and hold the Ctrl key and then click the button. Both commands are available in the Photos menu too. Alternatively, use the following keyboard shortcuts:

To create a mirror image of a photo, use the Flip Horizontally command in the Photos menu. To flip an image vertically, use the Flip Vertically command in the same menu.