Depending on the type of the input signal, click the DC voltage or AC voltage button, and select a proper range.
Click Run to start measuring the signal. Read the real-time voltage from the panel. While the instrument is running, you can change the measurement mode and the range by adjusting the settings on the panel.
You may hear clicking sounds from the NI ELVIS III while operating the SFP. This is expected behavior and is due to the switching of internal relays.