Step 1: Prepare the scene.
Before adding a new sky, I placed the ocean, island, and flamingos on separate layers, and then made a copy of the Flamingos layer so I could use it later. I clicked the eye icon on the copied layer to hide it for now. I then added a gradient as the sky on the original Flamingos layer and renamed it.

Step 2: Find a sky.
Choose a sky from the collection of photos in the Sky Replacement panel — or use one of your own. I provided a photo of a blue sky with soft white clouds that I think will complement the scene. To use it, click the down arrow next to the sky preview and then click the + at the bottom to choose the blue sky photo. Fine-tune the color and lighting of the new sky and drag with the Sky Move tool to reposition the sky where you want it.

Step 3: Add a sunset.
Make the scene dreamier with a sunset. To add a sunset photo below the blue sky, select the Flamingos and Sky layer and repeat the previous step. The skies won’t blend well just yet, but we’ll fix that soon. Photoshop places the editable sky replacement adjustments into a layer group; double-click the group name and rename it to keep things organized.

Step 4: Make a smooth transition.
Soften the hard edge between the two skies by creating a smooth transition between the blue sky and sunset. Select the Blue Sky group folder in the Layers panel and choose Layer > Layer Mask > Reveal All. Choose the Gradient tool and click the gradient preview in the Options bar. Choose the black-to-transparent gradient preset from the Basics category. With the mask selected, drag from the base of the blue sky to the middle of the large flamingo’s neck.

If this preset is not available to you, click the two color stops below the gradient bar and make sure both are set to black. Click the Opacity stop on the top left and set it to 100% and then click the Opacity stop on the top right and set it to 0%.

Step 5: Change the mood.
I added a Solid Color adjustment layer above the Blue Sky replacement to change the overall mood of the scene. Pick a light blue color (I chose #93C3D2), right-click the adjustment layer, and choose Create Clipping Mask to apply the color adjustment only to the Blue Sky layer group. Set the blend mode to Overlay to apply a styled contrast to the blue sky and layers below it.

Step 6: Bring back the flamingos.
Blend the flamingos back into the scene by clicking the eye icon to show the Flamingos copy. To adjust the crisp edges of the flamingo bodies against the background, select the Flamingos and Sky layer and lower the opacity to soften their cloud-like bodies.