sit about one arm's length, at about head level
then slowly cross your eyes until the 2 images merge..
then once your eyes are adjusted to the new 'focal' point, WHOA, it's really 3D. then relax and enjoy!
PS: first time very hard, after that it gets easy..
"If you experience fatigue or discomfort while viewing 3D images, cease use immediately. A ten-minute break is recommended about once every half hour. Switch to 2D immediately if 3D images still appear double after you have adjusted parallax. Individuals with a history of photosensitive epilepsy or heart disease or who are unwell or suffering from fatigue, insomnia, or the affects of alcohol should refrain from viewing 3D images. 2D display is also recommended for young children (up to the age of about six) whose visual system is still maturing and for individuals with notable differences in vision between their two eyes, who may find it difficult or impossible to observe the 3D effect. Viewing 3D images while in motion may cause fatigue or discomfort."