This screen will display a list of nearby Bluetooth devices that are in discovery mode as well as devices paired to the device. (howtogeek.com)
Others may go into discovery mode by default after you turn them on. (howtogeek.com)
To get into more detail, the right cup hosts a microphone, an on and off switch that boots into Bluetooth discovery mode when flipped on and held still for a few seconds. (techradar.com)