Place the Practice Image below in the center of your screen.
Sit about 24 inches away from your monitor and cross your eyes.
You will see a double image, (four dots/circles will appear).
Now slowly begin to uncross your eyes until the middle two dot/circles overlap each other.
You should see three sets of dots/circles.
Adjust your focus onto the "middle" set of dot/circle.
You should see the blue circle floating above the black circle.

If you have trouble with the above method, try the following alternate method:

Place index finger between and slightly lower than the dots/circle images.
Focus on your index finger.
Slowly bring your finger towards your nose
Stay focused on your finger, but pay attention to the background images.
(Instead of two dots/circles, you see see a total of four floating about.)
Continue bringing your finger closer to your nose.
You will see the middle two sets of dot/circles move towards each other.
When the two middle images are on top of each other, stop moving your finger.
You will now see three dot/circle images in the background.
The middle one contains the left/right images overlapped.
Slowly remove your finger from your field of vision.
Gradually force your focus onto that middle image.
This takes some practice to get used to doing.
You may need to relax and rest your eyes, and then try it again.