Mulitmeter

Hello everyone, so I was looking through the site and there are some great explanations on finding good ground, however for a novice like me that is pretty good with his hands and has done some cool installs, I havent ever seen or know how to use a multimeter to check the resistance for clean ground. I went out and purchase a Sperry multimeter, get home open it up and dont understand a damn word in the so called instructions.... So can anyone give me a step by step on how to use a multimeter and how I can verify the best ground. If you check any of my prvious posts I am having bigtime grounding issues with everything! I have tv's in my head rests and everytime the bass hits on a movie the ground noise is in my tv's. it is the most frustrating thing! there is so much ground noise that I have 2 amps and neither one is connected to speakers because of the ground noise.

I own a 2006 chrysler 300. the head unit is a pioneer avic N2. Thank you so much everyone.

Last question. I took my car into a al n eds to do the install BIG MISTAKE, and i learned my lesson! the problem is when they went to get power they cut into or spliced into the BIG main reb cable that comes off the battery in the trunk and goes to the car. REALLY THICK CABLE. I checked it out and noticed that the plastic/rubber is like half an inch thick. when I saw this I took all the electric tape in the world to wrap around this wire so that it would fill that splice in... makes sense? picture a 1 inch thick wire.... inside of the rubber (that protects the wire is half an inch thick) that was spliced into. I wanted to fill that hole that they cut the rubber so I did it with electric tape. Could this be the reason I have so much ground noise? how can I re-coat or protect this whole that they put.....

Begin HERE and read through the tutorial for a decent overview.

Where did you take your car for that installation?  Assuming you paid for the installation and you notice an unsafe power cable splice as you describe above, or you have severe ground loop noise, take it back and demand that they fix it.  Speak to the manager of the shop.

Here's a decent tutorial on multimeters: https://www.bcae1.com/vomillia.htm.

I'm willing to bet much of your noise is due to the Pioneer head unit.

The stereo shop tapped into your battery cables?  There's no reason for that.  They should have crimped a ring terminal onto your power cable and bolted it to the battery terminal.  Take it back and make them replace the cables and do it right.