Just extract into your main folder, if you look in your games folder and see another games folder you did it wrong.
When you run the game go into your load/save menu
it should look like this, with the cheat options, and Radioactive version clearly noted in the bottom left.
The install instructions are for either mac or pc. The parenthetical is to indicate where the "main" directory is for the mac, since its folder layout is a bit different.
The "main" folder for pc is whichever folder you've thrown SuperPowered into (where the executable lives).
