Post by David.
First, get comfortable.
Think of someone you want to write a story about. (example, David) Then, write down 3 or 2 things you know about them. (example, I like minecraft. I listen to music in the car. I have a lot of cousins.)
Make four boxes under the one that you choose. And then sketch out a little bit about what happened in each box. And then write what happened under the boxes.
Then that's basically it. You know the basics of making a story. Try it out.
For more ideas, find this book at your school library