It's very easy. Cut the usb cord from an old keyboard or mouse (or take it apart). Strip the red and back wires on the usb cable and on the 2 from your fan. Twist the wires together and cover each pair. You can even attach an adapter end like I did to make it modular.
I also use 4 hinges to keep the fan stable; hinges are cheap at home depot.
That is so cool! xD
I might do that with some coolers I have laying around.
Will come in handy for the summer to cool us off when we sweat at the computer xD