You have a power source - usually 12v batteries
You need to charge that power source - Alternator
, Solar Panels
, Wind Generator
You need to regulate that charge to protect the power source - voltage regulators
You need to distribute that power - wire
you need to protect your electrical equipment
or circuit breakers
Now there have been a lot of books written on the subject that go into great theoretical detail on the subject without actually telling you how to re-wire your boat. Mainly, because every boat is different
So, you can either buy a whole load of these books and get very knowledgable on the subject.
You can get hold of a wiring
diagram for a similar sized boat as your own, with a similar layout and copy it.
There was once (possibly about 10 years or so ago) a series of articles was done in one of the yachting magazines (could possibly have been Practical Boat Owner or Yachting Monthly). It was great - dead simple overview with big easy to read diagrams. In fact, it was so acclaimed they actually made a separtate publication of the whole series combined. I just can't remember the name or give you a link - maybe someone else remembers it