You have basic tools like a nice multimeter?
Sitting down with a VERY clear wiring schematic, and using a fine pointer, start at the battery and start following along. Wiring is very logical. Once you learn the various symbols (there aren't many on a bike) AND what they do, it all starts to click.
Start with a basic wiring diagram like how to wire up driving lights.
Does this make sense? If not, what specifically? I think if you can take small steps in understanding the big picture will happen quickly.
Once you figure out the various circuits, you can break them down into reasonable sections and isolate them. Just looking at a full schematic without understanding smaller blocks of it is intimidating.