As a not quite middle aged dude, I only just now figured out how to see magic eye stuff. I tried a couple times in elementary school but didn’t get it so I stopped. Had a few drinks earlier, stumbled on some magic eye pic that I could see clear as day and it blew my mind a little
I had a friend who couldn’t see them and the following explanation is how I got her to be able to:
Stand two arm lengths from the picture, holding you arm out in front of you with one finger up, so that your finger is halfway between you and the picture and lined up with near the bottom of it (or you could use any distance and put your finger halfway there).
Both the picture and your finger should now be in your field of view. Focus on the tip of your finger. Maintain your eyes in that focus state and shift your attention from your finger to the picture, remembering not to let your eyes change their focus.
Once you have your eyes stuck into that focus length you should be able to move them around and view all parts of the picture seeing the 3D effect. But if you still have problems you can move your finger to keep it in front of your eyes and in focus while you move your eyes, but you’ll quickly learn how to keep them in the correct state with a little practice.
This also works if you focus on twice the distance of the picture, but most people find the half-distance focus easier.