You should probably start by first figuring out what is in there and how they are used.
Get a general understanding of what each class represents and what each module is doing, or possibly why it's doing it that way.
A lot of the times, you only really need to change things in one or two classes, but you need to figure out which ones you need to change.
Also, help file will make a big difference when you're looking to the RPG module.
If you start making a game and getting a feel for game functions, then this might look slower in the beginning (as you won't be scripting until you've a good part of the basic game design completed), but later you'll automatically find the ideas what to script (when having an idea that need a new function implemented in the scripts) and you can see the results of your scripting afterward in your own game.
Understanding the editor and its limitations is one way to find some things to write, or how you should write them (especially handling user input). Most of my scripts are based on this.