Your story needs a setting. Where and when does this story take place?
Is the setting important to the story? If not, don't spend too much time on it. For example, if the story is about two rocks in a shoe box, you probably don't need to spend a great deal of time describing the box, since your reader can easily imagine what that looks like.
Sometimes the setting is so important that it resembles another character in your story. For example, in a story about a penguin trying to cross Antarctica, the bird might encounter 'angry winds' and 'desperate loneliness' of never-ending nights. In other words, the reader would sense that the setting itself has emotions just like the characters.
Here are some different ideas for settings:
The lake at the city park
The top of the Empire State Building
The school playground
A haunted house
Inside a rainbow
Your backyard
Write down some details of your setting on your worksheet!