There are two ways of viewing stereograms. The first one is to cross your eyes. I suppose that you use this way. In this way on the most of the stereograms the background is on the front. So if you want to see it correctly you should go deep in the picture with your eyes so that the focus to be behind the picture. You can try this first with your fingers. Put 2 fingers parallel and look something behind them. You will see that it is similar like crossing eyes. The more you practice the more you will be able to see them. I hope I helped.