Press the "Collect Data" button, which is pictured below.

A window will appear showing the values the sensor is reading.

Press the "Record" button when you want to record the value that the sensor is reading.

If you would like to close the graph without recording a value, press the "Cancel" button.

If you want to re-record a value, you can repeat the whole process by pressing the "Collect Data" button to start collecting data again.