You will need:
Draw a circle with a pencil. The easiest way is to make a mark with a marker at 12 and 6 o´clock. Place four marks evenly in the two halves. Then number the marks starting at 0 at the 12 o´clock mark and finishing with the number 9.
In the marks place the nails and hammer, one nail per mark. Tie the yarn to the top were the zero will be and you are ready to start multiplying.
If you don´t have nails you can use tacks. Or you can always draw the circle in a paper and do it that way. But is a better learning experience to have the wooden circle so they can create the patterns with the yarn.
Below you can see a different example of the wooden circle: