First off, you need to figure out which part of the process you want to contribute, as Mark himself stated there are very few people who can do the whole process on their own, either by lack of time or simply because it's just too difficult a task for most. Though if you think you can take on the challenge of doing all steps...
Do you like the idea of making the model? How about the textures or lighting? Perhaps you want to do whatever scripting is necessary for getting them in game? Once you figure out which parts you want to do, there are various tutorials in the BC Modding section where you can grasp the basics of a good few things.
For the meantime, all I can suggest is ask questions when you're stuck, or when you want to double check what you are doing. We have a huge community here all with knowledge in various things who'd be more than happy to help out.