You scroll through options until you come across animal parts and see a cow's udder. Curious, you drag the part to the model and attach it right on the stomach. A variety of options appear and you start to select a few.
You change the perception off except for you, meaning only you will know that it wasn't there before. You make the change sweeping, effecting all males. You make sure to click that the milk will be tasty and nutritional, and that the act of milking is pleasurable.
You then select the age of development for the udder at seven and finishing at 15, meaning you'll have a fully developed udder. You then turn off the private option, meaning the male udder will not be viewed as privates would. Finally you check societal change and make sure to leave the default state alone. You then click commit changes.
You feel a strange tugging sensation on your lower stomach and, like magic, a fully developed cow udder is lying in your lap.