[Al Skierkiewicz]

As Windell has pointed out, the wiper or the moving contact is labeled C. Depending on how you connect to A & B will determine if the voltage goes from 0 to 5 or from 5 to 0 as you move the handle. The diagram you need to follow of course, is the IFI RC Ref Guide which can be found on the IFI website.
In referring to the section of the RC ref guide, p. 8, terminal C would go the analog input at the top and terminals A & B would go to the +5 and ground pins using a PWM cable connected to the one of the analog inputs.