The following items are from the PC Gamer Magazine CD (Issue #169).

Contained is a multiplayer map building tutorial along with an example map called Arctica. To install the map, launch Arctica.exe and select your Crysis Game/Levels folder such as :
C:\Program Files\Electronic Arts\Crytek\Crysis SP Demo\Game\Levels

(at least this is what I could figure out without any instruction from the PCG CD)