@flip9- Well explained
Some 'caveats' about fuse taps-
Never tap into a safety-critical fuse. Some examples would be "Airbags" (sometimes called SRS), "ECM" or "PCM" (car engine computer), "wipers", "ABS", or any external lighting including brake lights. While a properly installed fuse tap should not be a problem with these, strange things can happen in life and a fuse tap is adding a possible point of failure. There are almost always safer fuses you can tap to get the needed power requirements.
Among other fuses, don't tap low-rated fuses (say 5A or less) as doing so can possibly overload the car wiring.
Keep your wiring tidy and secured where no possible movement of people in the car or movement of any car part (like doors) might cause problems such as pulled or pinched wires. This includes not running wires across sharp edges.
If you make a wire-to-wire connection, either solder it or use a crimp-type connector, then use electrical tape or heat-shrink tubing to insulate the connection. Also, if you make this kind of connection on a multi-wire cable, stagger the connections so that if the entire cable pulls loose or the insulation fails it will still be impossible for those wires to short against each other.
Lastly, if you are not certain that you can do the job correctly, then enlist some help from someone who can or let a pro do it for you. Car audio shops are good with this kind of thing though any mechanic should be able to handle it too.
Phil