Most good hobby stores will carry the tools and instruction books that you will find useful. A few words about safety never allow a child to use the tools unsupervised. The tip is very hot and can cause severe burns if proper care is not taken. You should also insure that a supply of water is available in case of accidents. Make sure children are taught the proper operation of the tool, and the safety precautions.
Eye protection is a highly recommended safety precaution to take.
As with any other hobby, practice will increase the enjoyment and the skill. The tip can create very a fine line, or dark shading depending upon how much pressure is applied and for how long. Practice something simple initially, perhaps writing your name on a scrap piece of wood, try to write your name with uniform dots, or lines that are darker on one side as if in shadow. Wooden fruit crates when taken apart and sanded make excellent practice pieces. The slats are small enough to be easily handled, but at the same time are large enough to allow your creativity to shine through.