Try downloading one of the sheets the community has (see wiki for a list of community created sheets) that closest fits with the game you have in mind. Look at the code and play around with it. The wiki has tons of information, provided you are mentor level , on how to create sheets. The reason you most likely need mentor level access is because the API is really handy in making sheets, and it's only available to mentors. If you are just trying to use one to create a character, I'm sure pinging the character sheet thread would be a great place to start :)
