One way could be to have a clear resolution of the main conflict and a sense of closure for the characters. Maybe a happy ending or a bittersweet one that leaves a lasting impression.
You can say 'el cierre' too. But 'el final' and 'el fin' are more frequently used. It depends on the context, but in most cases, either of these would work fine.
They might use 'y así se acabó' which means 'and so it ended'. The use of 'acabó' here gives a sense of finality. It's a simple yet effective way to emphasize the end.
Well, 'fin' by itself is also used to denote the end in a story. It's simple and straightforward. For example, when you finish telling a story, you can just say 'Fin' at the end. Also, 'acabar' can be used in the sense of 'to end' for a story, such as 'La historia acaba de esta manera' (The story ends in this way).
At the start of a Spanish story, you might use phrases like 'Era una mañana soleada...' (It was a sunny morning...). In the middle, you build on the story. Let's say 'Mientras caminaba, se encontró con un animal misterioso.' (While walking, he came across a mysterious animal). For the end, you can end it positively or negatively. If positive, 'Después de muchas aventuras, el protagonista se convirtió en un héroe.' (After many adventures, the protagonist became a hero). If negative, 'Pero el animal lo atacó y el protagonista no sobrevivió.' (But the animal attacked him and the protagonist didn't survive.).
In the beginning of a Spanish story, it often sets the scene or introduces characters. For example, it might say where the story takes place or who the main character is. In the middle, there is usually some sort of conflict or action. This could be a problem the character has to solve or an adventure they go on. At the end, the story resolves. It could be a happy ending where the character achieves their goal, or a sad ending where they don't.
In the world of Spanish 1, there was a family of mice. There was Papa Mouse, Mama Mouse, and three little mice named Tino, Tina, and Tito. One day, they heard that there was a big cheese festival in the next village. They decided to go. Along the way, they had to cross a big river. But they were smart. They found a big leaf and used it as a boat. When they got to the festival, they ate so much delicious cheese that they could barely walk back home.