1 Bring your foreground exposure and your sky exposure images into photoshop elements
2 go to the sky exposure image and Select all (ctrl-A), then copy (ctrl-c)
3 go to your foreground exposure image and paste (ctrl-v)
the sky exposure will now be on a layer above your (background layer) foreground image
4 make sure the sky layer ("layer 1") is selected in the layers palette and click "add mask" icon at the bottom of the layers palette.
5 Select gradient tool (press G), in the toolbar along the top click on "edit the gradient", select the 3rd square in, "black to white" and press Ok.
6. make sure the layer mask is selected in the layers palette next to your sky, layer 1, (just click inside it with the mouse) then click on the horizon line or just above in your image and drag down an inch or so
This will mimic a Neutral density graduated filter. Depending on where you click and how far you drag will affect how hard the "grad" is and where it starts/stops. If you dont like the first effort you make, just click and drag again shorter or longer.
If it comes out the wrong way up, just drag up instead of down.
You can then tweak the grad line(mask) if desired by selecting a brush ('b') and painting on the mask to hide/reveal select areas as you desire using black or white.
HTH
