Go to the mods folder and open the 'base' folder. Here you'll find a series of .txt files explaining each of the mod files.
I suggest making a copy of the 'Base' mod folder. rename it, and start playing with it. You can also use the 'WeirdBiomesMod' as an example. If you have more specific questions you can open add a new thread in the community forum and I'll answer with more details.