Basically, the easyest way to run pc fans is via a phone charger/battery charger. I have found that a good r/c car battery charger puts out enough power to run two fans. Say you have a phone charger, cut off the phone adaptor bit at the end and then strip about 1cm of plastic off of the wire.

There should be one black and one red wire. On the fan do the same and there should be 1 black and one red wire. There also might be a yellow wire, just tape the end up it is not needed.

Then simply connect red to red and black to black. You can either solder them together or just tape it. But make sure you dont touch the chargers red and black wires together whilst its on, or else sparks will fly :d

Hope that helped.