To install:

Copy to 

C:\\...S.T.A.L.K.E.R. Clear Sky\_appdata_\savedgames or

%PUBLIC%\Documents\STALKER-STCS\savedgames\
C:\Users\Public\Documents\STALKER-STCS\savedgames\ (Windows)

%USERPROFILE%\Documents\Stalker-STCS\savedgames\
C:\Users\[user name]\Documents\Stalker-STCS\savedgames\ (GOG)

[Steam folder]\steamapps\Common\STALKER Clear Sky\_appdata_\savedgames\
C:\Program Files (x86)\Steam\steamapps\Common\STALKER Clear Sky\_appdata_\savedgames\ (Steam)

Author: Real Slim Shady