Here are two correct and simple ways to say your idea:
- People join the stars in the sky to make pictures called constellations.
- People imagine pictures by joining the stars in the sky, and they call those pictures constellations.
Why these are better (easy steps):
- Start with a capital letter: "People" not "people" at the beginning of a sentence.
- Use "the stars" to talk about the stars in the sky.
- Say "they call those pictures constellations" or use "called constellations" so it is clear what "them" means.
- Keep the sentence short and simple so it is easy to understand.
Example: Orion and the Big Dipper are pictures people see when they join the stars.