[APML]: Stacking images in photoshop

["Bobby Middleton" <bobbym@webwide.net>]

I'm stumbling through my first attempt at digital double-stacking in
photoshop. I am going by the instructions posted by Wallis and Provin on
their web-site article titled "Stacking Images in Photoshop." I have pretty
well aligned and sized the 2 negs per their cropping 
instructions and have created a new layer of one of the images. The next
step is to copy and paste the other image into the newly created active
layer. When I try to copy and paste under edit, the copy and paste options
are greyed out. What am I missing?
Please be aware that my further success will depend on how idiot proof your
instructions are!

Bobby Middleton