This was done using the multimeter device at TechShop San Jose. They have an electronics workstation with multimeters, soldering iron and other tools for working on electronics.
Set up the multimeter by turning it on. Plug the black probe and red probe into the spots shown in the photo. Turn the knob to 20 V- as shown in the photo.
To test a battery, hold the probes, one in each hand. Touch the metal tip of black probe to the battery's ground or negative end, marked with "-". Touch the metal tip of the red probe to the battery's positive end, marked with a "+". Make sure the probes have good contact with the ends. You can use your fingers to press the metal tips of the probe to the battery.
The voltage read out will display on the multimeter. See the attached photos for examples of battery test results.