Everyone writes/configures their own script however they want, including NPCs, mobs, items, spawns, etc. Questions like this are at the very least quite strange, especially when the Wiki already contains all the necessary information on how to set these things up.

Please make sure to read the Wiki before creating a topic in the future. Threads with questions that are already clearly covered there may be closed.

Also, this was submitted as a bug report, but it is not a bug. Please use the appropriate section/category next time.