Unzip the mod and and find the main mod class with the @Mod annotation.
There should be a method like this:
@EventHandler
public void preInit (FMLPreInitializationEvent e)
{
}
In this method, add a line that looks something like this:
GameRegistry.addShapedRecipe(new ItemStack(Items.diamond_pickaxe, 1), "XXX", " I ", " I ", 'X', Items.diamond, 'I', Items.stick);
You have to change the parameters so that it does what you want.
If you don't know what I mean, give me the recipe and I tell you exactly what to type.
