Currently the engine uses fbx sdk 2012 which isn't avalable anymore which means the engine wont compile. If you want to give a shot anyway you can find the sdk here: https://www.autodesk.com/fbx
Other than that, here is almost everything you need to build Amnesia: The Dark Descent. Included are project files for Visual Studio 2010 and CMake for Linux & macOS.
We encourage everyone to contribute code to this project, so just sign up for a github account, create a fork and hack away at the codebase.
All code is under the GPL Version 3 license. Read the LICENSE file for terms of use of the license.