We first use the Composite Transform to align the smaller white image with
the lower left corner of the larger black image.

The input image is the 780x540 black 8-bit image.
The Overlay image is the 744x504 8-bit white image.
Use a 1-point shift for the Alignment mode.

The default positioning of the alignment points is at the lower left of the
(output) composite image, and rather than try to move them around by hand,
I'll leave them there and reorient the mask image later so that the drop shadow
ends up in the correct place by the time we are done.

Do not click the "OK" button, because we will use the transform a second time.
Just click "Apply." The image produced will be called Mask1 in the next pages.