Connect the electromagnetic pickup / driver to the outputs of the wave generator.  Use the Pasco wave generators as they will limit the power into the pickup to 10 Watts so as not to burn it out.  Also take the output of the wave generator and run it to the amplifier so that the driving frequency applied to the pickup can also be heard with the speaker.  

Pluck the string on the Sonometer to hear the sound and then adjust the frequency of the wave generator to match.  When you find the right frequency the string will be driven by the pickup to vibrate with a large amplitude.  Use the Flexcam which can focus at very short distances to view the string vibration.