Its done the same for cartomizers or attys.
Set your tester for testing resistance (how to do that depends on your particular tester, but if you're unsure, check the manual that came with it). It should be reading all the way to the top of the scale. Now touch the two probes to each other. It should read 0 ohms. Once that's working, place one probe on the
threads being careful not to touch the center of the atty/carto with it. Then touch the 2nd probe to the center connector. It should read the resistance of that particular atty/carto (usually about 3.2 ohms for a standard atty/carto).