Unzip,then copy gamedata folder to your game folder.
A new utility to make mod installation simpler and cleaner is being demonstrated on Steam Greenlight. S.T.A.L.K.E.R. Mod Player lets you install and play mods for the S.T.A.L.K.E.R. series games. This streamlines the task of extracting zip files into different directories, editing configuration files, etc. and reduces installation of most mods down to the click of a button. Since there's less hassle to cleanly add and remove mods, you can freely try out new mods with no trouble.
The system is shown powered by Steam Workshop. You can check out the Greenlight page here.