Here's some tips how to view stereograms:
Basically you need to unfocus your vision and look through the stereogram. This makes patterns to overlap and gives each eye slightly different view, and that makes you see 3D image.
Get any still stereogram for training purposes or use the one on the bottom of game's Intro screen.
Look through the stereogram imaging that it's transparent. Your eyes should be relaxed and not focused on stereogram. When your sight is blurred try to move closer and further toward the stereogram, and do it very slowly. At some distance you may notice something happens and blurry relief may start appearing behind your screen. It'll be blurry, the next step is to make it sharp.
Try not to switch your sight onto the image - look through it all the time. Hold your head horizontally, don't tilt. Also try not to blink. It may take a little while until eyes focus properly by themselves. Do not force it because you gonna switch to 2D image. Eventually hidden image will become sharp and clear like a reflection in the mirror.
If you see a hidden image but it looks inside-out, it means you cross your eyes. You need to diverge them instead. If you see doubled objects - it means you diverge them too much (doublefusion), try to refocus.
It may take a while, so be patient and do this couple of times with different stereograms. It really worth it!
You may experience some eyestrain and even headache at the first time. It's ok and won't hurt you. It's also a good exercise for your eyes' muscles.
If you still can not see anything and wonder how it may look, try this online tool - Reveal the Magic Eye
Good luck and thank you for trying!