The 'cross eyed' method to view 3D images with the naked eye.
1) Make sure your head is level and the image to be viewed is centred straight ahead at a comfortable distance.
2) Relax your eyes and then cross them so that the twin images are doubled to 4.
3) Relaxing your eyes, allow the images drift back together until they overlap forming a single central image and 2 outer images.
4) At this point you may need to gently tilt the head from side to side until the central image lines up.
5) When the central image of the 3 is seen in 3D you can then 'look around' this image.
Using this method, the left eye's image is in on the right and the right eye's image is on the left. It is important that the eyes are relaxed, because, in effect your 2 eyes are converging on a different plane to that on which they focus individually. The eyes are being used in a similar way to when viewing 'Magic Eye' images, so if you can see these, then you've part trained yourself to see steroscopic images. The facility improves with practice.