It takes a few times to get the hang of filling the mold to make them 'perfect' balls. There's a small hole in the top of each cavity. Fill it up as far as you can, then move the mold to the freezer. Make sure it's flat in the freezer. Use a measuring cup with a pointed spout, add extra water through the hole in each cavity. There will be some excess water on the top around the outside mold, but once it's frozen it will break off easily.
The ice mold is worth your purchase