The powered hub provides power the "output" of the hub to power your peripherals (keyboard, hdd, etc.)
You still need to get 5Volts to the 770. What I did was take my hub apart, and solder a small jumper from the 5 volt line on one of the "output" ports to the 5V line on the "input" port. No special cable required. Others have used cables, like the one you linked to, to steal the power from one of the outputs. This is probably safer if you are not comfortable with modifying your hub.