Another method for 3D viewing is called cross-viewing or the cross-eyed method. You aim your eyes so that the lines of sight of your eyes cross in front of the image. When you cross-view, the muscles inside your eye that control the focusing lens contract strongly and shorten.
The Single Finger Method
You'll need to aim your eyes in front of the 3D image. You'll use your finger to help you figure out where to aim your eyes.
Bring your forefinger up about six inches in front of your nose. Focus both your eyes on it.
While focusing on your finger, notice what has happened to the circles on the screen. You should see four circles. Keep focusing on your finger, but at the same time observe the four circles on the screen.
Move your finger slowly toward the screen (still focusing on it!) until you see the two middle circles slide together and merge into one figure. The combined figure is composed of two concentric circle. The inside circle pops toward you in 3D.
You are using your finger to help you. Make a subtle shift of your attention from your finger to the figures when you find the right focal point. Get your finger down and out of the way once you get the combined 3D figure.
This takes most people several tries, especially the first time. If you have problems, play with the positioning of your finger and the shift of attention from your finger to the 3D figure. Slowly move your finger back and forth until you find the position that gives you the 3D image.
At first, the 3D image might come in blurry. Relax a little, give your mind a chance to organize itself and the 3D image should come in sharp and clear.