First of all, think of a jolly good story that lots of children will want to read. And when you've done that, write it down somewhere - like a piece of paper or a computer - being careful to avoid any spelling mistakes. Make sure you have lots of interesting characters, some cracking descripions and a watertight plot, and be extra careful to make it so exciting that your reader won’t ever want to put it down, not even to go to bed.
And then, when you’ve done all that, send it to a publisher and get them to publish it. Or better still, publish it yourself. Sell it to lots and lots of children, and grown-ups too if you have the time, and then when you’ve sold hundreds of thousands of copies you can call yourself a best selling author.
Here are some other HOW TO ideas...