Once you've aligned it correctly, let's darken this image up a little bit. So again we will do Image > Adjustments > Levels (Ctrl/Cmd+L). Change the value to 40 / 1.00 / 255.

Step 5 - Landscape Placement

Now it's time to correctly place your landscape image. Drag this layer and put it underneath your "Door Layer" copy. We want to align it with a little bit of grass right above the door. It should like this this.

Step 6 - Adding the second sky

Now we are going to start adding a gradient like sky transforming the cloudy sky into a galaxy looking sky. We now need to open the image "Skylight". It also has a high resolution, so we will have to Scale this down a bit. So do Image > Transform > Scale (Ctrl/Cmd+T). We only want to scale it enough to where it's still covering most of the composition at this time. It should look like this.

We don't need all of this, we just want the top white to blue area. So we want to use the Rectangular Marquee tool (M) to select the stop area of this. Once we've selected it below. Inverse the selection by doing Selection > Inverse. Use the Eraser (E) to erase the outside. Then unselect this layer (Ctrl/Cmd + D)

Once erased, it should look like this. Align it like so, just barely between the tree's and sky. You want to keep the very white/bright part of the sky near the tips of the horizon tree's.

Now lastly, move this layer under "Door Copy", but above "Landscape". Set this layers mode blending mode to Multiply. The composition should now look like this.

Zoom in on the compostion where the two layers meet. You'll notice you can still see the hard edge of the "Sky" layer. Take a eraser tool (E)

Step 7 - Add the galaxy to the sky

The sky's a little dull, so let's add some dazzle to it. Open the image "Nebula.jpg". And resize it a little to your liking. You can choose how much of the cloud you want to show up. After you resize it, you want to make the cloud horizontal. Use Image > Transform > Rotate and rotate the image until the cloud is horizontal.

Next let's put this layer behind the "Door Copy". Move the "Nebula" layer beneath your "Door Copy" layer, but make sure you keep it above the "Sky" and "Landscape" layers.