Viewing Mirrored Images with Single Monitor

Display your image in side-by-side mode and press the 'E' key to set the image spacing to wide.
The key toggles through narrow, medium and wide spacing.
You can set 'wide' spacing as your preferred side-by-side format in Edit/Preferences.
As images can only be reduced to 50% in size with the menu settings, large images may be reduced further by rotating the mouse-wheel towards you.
It may sometimes be necessary to view side-by-side images that have one side mirrored and which are intended for special viewing methods.
Also, you may wish to share your stereo images with others who cannot freeview and do not have anaglyph glasses.
You can view these with a single monitor using the arrangement below:-

This example has the left-image mirrored.
To do this, press 'Shift+F9' or choose 'Stereo/Side-by-side/Mirror left' from the menu.
Place a mirror about 125x125mm (5"x5") square against your nose and view the right image with your right eye.
Focus your left eye on the right image but carefully adjust the angle of the mirror until the reflected left-image merges with the right one.
A surface-silvered mirror will be preferred by the stereo-enthusiast but the ready availability of ordinary, back-silvered household mirrors makes this a simple way of encouraging interest in stereo-imaging among the 'general public' .

See this article and also this .