Fuse box is not the main distribution point.
Tim's trying to help you on two fronts. And he's right to do so.
Concept of electrical power.
Power is the combination of voltage and current.
Voltage is the potential to flow. There can be voltage even if there is no flow. For example when the engine is off, every wire attached to the battery psoitive has the same voltage. Go measure the voltage from ground to battery positive, and then ground to the alternator output stud (marked Bat). Both will be 12.5 Volts. It's like having a a well pump and water tank on the roof of your house. With all faucets closed and the pump off, there's pressure at the tank outlet.
Current is the amount of flow. Open the faucet in the sink and that pressure sends 5 gals per minute through the pipes into the sink, and from there to ground.
It wouldn't hurt to learn this stuff. Here's a Chrysler A/V about it
1963 Fundamentals of Electricity and Magnetism from The Master Technician Service Conference Series (Session 184)
The other part is how to read a wiring diagram.
Start at the high voltage source.
If the engine is running that's the alternator; if its not running then its the battery.
(Because the alternator output is regulated to roughly 14.5 Volts, and at best a battery will be 12.8 or so. (It will float a little higher but as soon as current flows its going to drop.)
Tim's explained how the lines represent wires and dots are connections.
and there's more here.
Electrical Wiring (Session 247) from the Master Technician's Service Conference
