What do the pigs reveal on pg. 23 of Animal Farm? What is the first act using this new skill?

In chapter two, the pigs revealed that they had taught themselves to read and write from an old spelling book that had belonged to the children of Mr. Jones. Technically, the first thing that they did with their new skill was to change the sign from "Manor Farm" to "Animal Farm." However, the more significant action was that they wrote the seven commandments on the wall of the barn.  These commandments outlined what were prohibited activities among the animals and included anything previously attributed to human behavior such as sleeping in beds, and wearing clothes.  Most significant was the first commandment which read, "Whatever goes upon two legs is an enemy."  This solidified the fact that animals and humans were never to be allies, and also set the stage for the pigs to later change the commandments to suit their needs.