For resistance, set the mm to "ohms" (note you must set the scale, most likely 20). Grip one clip around the
thread of your carto/ atty, keep the other clip closed and touch the centre post. You should get a reading. Just make sure that the clip touching the post doesn't touch the
threaded part.
For voltage, set the mm to 20 V dc. Put one clip on one end of the batt, and the other on the opposite end. You should get a reading.
For proprietary batts (like the ego or kr808) you're going to need new probes I think. But it may work. Similar to testing resistance. one clip touching the thread, the other touching the post. Make sure the clips don't touch each other.