Telling a Story

I am really going to do it hopefully)! About a year and half ago I had the most basic idea for a story. It mostly revolved around an image in my head teenage girl in a suit of armor and her brother riding a wolf. The basic point of the story is that the boy had originally tried to be a warrior while the girl wanted to be a magician, but they found their paths in life switched. With the boy becoming a great wizard and the girl a mighty warrior. For what ever reason I have really been thinking about the story A LOT for the past two weeks. I now know that it takes place in a hidden kingdom that lies in a valley that has been made inacessible from mountains. In this kingdom live Dwarves and humans, and while dwarves are the majority, ancient prophecy state that as long as a man holds the throne, the kingdom will never fall. However, an evil warlock who is in league with the Dark Dwarves (dwarves who live deep under the mountains, and are evil), has a plan to murder the king and place a prominent Dwarf on the throne. In his plans an inevitable civil war will erupt, but with the help of the Dark Dwarves his side will win, and he will be the pupeteer pulling the strings behind the dwarf king. He believes that he can not fail in this due to a prophecy: When the true King is dead, he who commands the wolves, will come to power, creating a New World. Yet, forfeit his crown will be to the Golden Warrior. The Warlock believes he is the one who commands the wolves, believeing the wolves to mean the Dark Dwarves, yet he knows not who the golden warrior is, and thinks that is the only person who can stop him. After his coup attempt, the heir to the throne, escapes, and the Warlock now believes him to be the Golden Warrior. The heir flees to a small Abbey where two orphans, a brother and sister live. When the Warlock's army comes the two get seperated and begin down their own paths of self discovery. The boy learns true magic and befriends wolves, while the girls learns she is a natural with a sword and posesses a tactical mind. The two get back together at the end, and defeat the Warlock. The heir is killed in the battle and the crown is given to the boy, but he willingly gives it to his sister because she is better suited to rule (and she is a blonde, hence the "golden warrior"). That is the plot in a nutshell. There is a lot more to the story obivously, but as I continue to think about it I realize that if I were to write this it would be a full-fledged novel. Chapters is the only way to tell the different aspects that are woven together into one story. The problem is that I have never even tried writing something novel like (I wrote a story once that could probably be considered a Novella, but that is about it). However, I can not get this story out of my head and I really want to write it. As soon as I get more pressing written works out of the way (like the picture book about our trip to Scotland), I want to try writing this story, because I don't think it is going to get out of my head any other way.