If you haven't already downloaded the latest Radionics guide, do so. Spooky Radionics V1.1 Operational Manual Edition 2.
In the Dowsing section, page 19 is an explanation of how to use the Pendulum.
The Radionic Pendulum: https://www.youtube.com/watch?v=raXvzPqsoY4
For more details, please check the link: