Help getting a custom story to show up. (Steam Ver)

[Your Computer]

Now Im about to try and just unzip it in the custom story folder.

That's the normal way of installing a custom story. If the custom story requires you to extract its files on top of the root folder of Amnesia (e.g. if it includes a redist folder or multiple folders to be spread throughout the Amnesia directory structure), that means the custom story has a complicated installation and probably wasn't organized well (full conversions being the exception, kind of). (Note: redist folder is found for retail, non-Steam version of the game.)

It'd be easier to help you if you tell us what story you're trying to install. As an alternative, you could try using Desura to install custom stories available on Desura itself.