Relay configuration is read from the file $XDG_CONFIG_HOME/usb-hid-relay/config.yaml (usually ~/.config/usb-hid-relay/config.yaml). This YAML file should contain a ...

The app opens a Tkinter window. Pick the COM port for the USB-RLY08C, click Connect, tick the channels you want to act on, and use the per-channel toggle buttons or the Turn Selected On/Off buttons to ...