The Monarchy Countries?

I have a very important project due in about a week in History. It is mainly about making your own county. And, mine is going to be Monarchy. I hope this makes good enough sense so the question can actually get answered, but. I have to have someone make the Laws. Someone that enforces the Laws, and lastly, someone to interpret the Laws. So far, I have heard that Monarchy Countries are very different from the others, so, can, I just go and make anyone in charge of them just like that? Or do I have to do it a specific way?