Extract the contents of the relevant folders to where you have installed the contents of your base PsychoStats root and www folders. You will not be able to run the PsychoStats install or PsychoStats itself until you have installed support for a game. If you wish to install support for multiple games you will need to create a separate PsychoStats installation for each game.
If you wish to change a PsychoStats installation so that it supports a different game you can simply copy your new game files over the old ones. When you do so your PsychoStats will only support the most recent mod you installed, and you can safely delete game and mod specific images and themes for the old games and mods. You will need to drop and recreate the database if you install support for a new game or mod.
You should always install the base PsychoStats files first, then extract the contents of the "root" and "www" folders to the folder where you have installed the base "root" and "wwww" folders. You should extract the contents of the game folders after you have extracted the base PsychoStats files and overwrite any files or folders you are asked to.