Answer:
You can describe the sunset using the five senses.
Sight: What colors are there? Vibrant pink? Dull blue? Blinding white? Also mention the shapes. Do you see a perfect sphere (the sun)? Wispy clouds? Pinpricks of stars appearing?
Hearing: Is there wind in the background? Is it quiet as everyone falls asleep? Do you notice your own breathing?
Smell: Kind of hard, but depending on the time of year, you could mention the smell of flowers, freshly cut grass, or fireplaces burning.
Taste: Harder than smell - maybe you could mention food you've been eating or something cozy you've been drinking while you watch? You can skip this sense if you want.
Touch: Describe where you are. Are you sitting on fine dirt? A scratchy, fraying lawn chair? The rough roof? Also mention the temperature - are you shivering from the cold or sweating from the heat?
Try to come up with your own descriptions and don't forget to use a lot of adjectives! Good luck!