Install guide:
1) Download the file and put it somewhere safe.
2) Go to the folder where you installed the demo to, and then go the folder below. Assuming you installed to drive C, it will be like this:
C:\Program Files\Electronic Arts\Crytek\Crysis SP Demo\Game\Levels\island
3) Find the file called "Level.pak" and back it up somewhere safe, or just rename it.
4) Copy the file you downloaded, into that folder.
5) Play the game as normal.
6) Keep saying, Wooooaaaa coool!!!!!
note: The game still starts as normal so you might not think it worked. But when it goes from night to daytime, you'll start noticing differences. And when you get down onto the beach for the first time, look to your left