How did areis become a constellation?

Answer 1

Greek guys saw it in the sky and gave a name for it.

Answer 2

Aries became a constellation in ancient times as part of the zodiac, representing the ram. The pattern of stars that make up the Aries constellation were given this name by early astronomers who associated it with the ram in Greek mythology. Over time, the position of the stars relative to Earth formed the recognizable figure of a ram in the sky.