Need help on wiring external SERVO to P2

[snowmaker55]

I would like to add an external servo with mechanical off-load hook to drop cards with prize numbers printed on them. Im good with the mechanical release portion, but need help with what specific wire I can use to control the servo. I know I also have to add a 12v to the servo to. I have an up/down gimbal pan pot on the back of the Xmitter, so figure I can use that channel, you think??... All of your comments are appreciated