Now we need to apply a slight Gaussian blur to our image. This will enhance the 'depth' of our dispalcement map. Go to FILTER...Blur...Gaussian Blur and apply a blur of between 0.5 and 1.5 px.
This is your 'map'. Save it as a .psd document (not .jpg). FILE...Save as... and name it map.psd. Save it to your desktop so you can find it easily later.
Now, to return to your original image, go to EDIT...Step Backward. Repeat this one more time.
Now you need to introduce your 'poster' to this stage. Open the one referred to above and resize it (EDIT...Transform...Scale).