1. Use the Transition Measurements Function to get the end time of the rising and falling edges. You will need one for the rising edge and one for the falling one. This function can be found by going to the Functions Palette >> Signal Processing >> Waveform Measurements.
2. Connect the waveform wire to the signal in terminal of both VIs.
3. Select the direction of the edge by creating a constant or control at the polarity terminal, by default it is rising.
4. Wire the Measurement Info of both Transition Measurements VIs to an Unbundle By Name Function and select end time by left-clicking on it. Depending on your application requirements you can select the start time instead of the end time.
5. Use the Subtract Function to subtract the end time of the rising edge from the end time of the falling edge. This will give you the resulting pulse width which you can view by placing an indicator at the output.