Hopefully, most of the information you require can be found on this diagram:
Also by the throttle there is a little red button that does nothing when I press it. What is that? Cruise control?
As a side note is possible to make the horn switch into a off/on switch? or is that what the red button is for on the throttle?
Yes, the round red button next to the horn button
is for the cruise control.
The horn button is only a low power momentarily closed switch, so it would not be much use as a power switch.
As it is already connected to battery +
(and I don't have a horn) I have wired mine as a headlamp flash button instead.
The square red light switch on the throttle is not suitable for switching or carrying high currents, but is ideal for the high voltage LED lights that are available as accessories.
Alan