In the Placing Conditions panel, first un-check the Ignore All feature.

Next, let’s make our Altitude Range extend from 0 (low) to 140 (high).

Change the Slope Angles Range to 25 (max); leave (min) at 0.

Check the results in the Camera View.

Now let's alter the Sky Gradient property.

We need to change the default color settings in the Ramp Layer. Select Ramp Layer in the Scene Tree and then Color Gradient in the Property Tree. The Sky Gradient Editor will open.

The color on the left hand of the gradient represents the sky at it’s deepest blue directly overhead; the left-hand gradient color represents the sky at or near the horizon, where the color is lighter.

Click on the Key Creator Pencil button.

Now click on the Color button. This opens a standard Windows Color Picker. For the Zenith color, choose a dark purple color and click OK. The selected color is now ready to apply to the Sky Gradient. Click once above the Zenith color key (the small triangular marker on the right). The new color is applied to the gradient.

Repeat this procedure to set the color for the Horizon color key. Use a lighter color.

Now let’s soften the gradient itself. Change Gradient Depth from the default value of 18 to 45.