Hook the dome of the Van de Graaff to the top plate and the base of the Van de Graaff to the bottom dish.  Gently blow on the ball through a straw to start it rolling if it doesn't start by itself.  The rolling of the ball is what transfers the charge between the two plates.  The unit will have to be very level for this to work properly.

Better control of the electrostatic potential can be had when using the Wimshurst Machine.  Much less arcing between the top and bottom plates of the unit will occur. 

ACCELERATOR OR CYCLOTRON MODELS:  The racing ball unit, graphite ball and dish unit, and the gauss rifle (5G10.55) are all examples of linear or circular accelerators.

Level the dish of the graphite ball and dish unit.  The Static Genecon is best for this unit, but the Wimshurst will also work.  Build up some electrostatic potential and then gently blow on the ball through a straw to start the movement.  The ball will continue to move as long as the electrostatic potential is maintained.  Note that the ball of this unit will move at a much slower rate than the that of the racing ball unit.