then try to make a folder whats called Tenebris Lake in the custom story folder and put erverythink in there but you need to change the lang file to extra_english and put it in to Steam\SteamApps\common\amnesia the dark descent\custom_stories\Tenebris Lake and try to start it as a custom story but then you will not have the new lantern that i made 

 xD hope that will work for more questions ask me.
 after that you need to create the custom_story_settings it shall say this.
<Main
	Name="Tenebris Lake"
    Author="Bori's Game Studios"
    StartMap="01_lake.map"
	StartPos="PlayerStartArea_1"
/>