OK on the bottom of my voltmeter is 3 places to put my 2 leads. On mine the center is always the ground black. If the red lead is in the right hole then I can test for voltage & Ohms resistance. When in the left hole the red lead can now test for Amps. In the pic I set the dial to read 10 Amps (max). I can't crank the engine or even run the headlites as its too many Amps. But it is useful to find a small electrical drain. Now I unhook the pos. battery cable and move it over and hold the black lead on my voltmeter to the + batt. post and the red to my + battery cable which is not touching the batt post. This puts the voltmeter in series with the + battery post & + battery cable. If there isn't any drain the voltmeter will read 0.00 and thats not the problem. If there is a reading (even 0.1 of an amp.) you have a small drain & you should see it on the voltmeter. Now go through your electrical system one circuit at a time and remove a fuse and check the voltmeter. The voltmeter will go to zero when you have found it (if thats your problem). then you need to figure out why. Bad headlite switch, or a short or ???