When you want to throw a Gnome far, try to get a little close to the leaves by the pond and between a fern. It is a few of steps away from Fred and George. Start spinning, then when you are going fast, let go. The gnome should go far. Note: This may require some practice. Do not spin too long or you will get dizzy.

It seems that you spin eight times before you get dizzy. Also, if other gnomes hit you, you may throw them twice as far.

On the last day, go down by the lake. There will be three bushes. Three gnomes should be running back and fourth. Hit one with the Stunning Charm and pick it up. Throw it in the lake. Do this with all three of them. After you have thrown all three of the gnomes in the lake, a chest should appear with a Famous Witch And Wizard Card.