I still don't get the sense of this...

These first two aren't good examples as the pic quality is kinda blurry. You have to cross your eyes to blur the images and they will seem to start shifting. Then try to line up the pics so a "third" middle image appears and hold it there once the things are lined up and it should work. If you can't, then don't wory. Just practise a lot. Of course, there are some who simply can't cross their eyes, so they will not be able to see these unfortunatly.

This also requires getting your head tilted side to side just right to line up and fuse the images.