The first thing to understand is that different colours require different voltages eg white =3 volts red = 1.5 volts.
So using a 12 volts dc battery you will need to included a resistor to drop the voltage to suit the led being used.
There is a lot of info on the Internet on how to calculate resistance value.
With reference in how to wire them, just wire them in parallel in groups that you want to switch. Supplied from the battery via a fuse.
With reference to general lighting on the boat you could wire 4 white leds in series , this would remove the need for resistors. This works by dropping 3 volts across each leds.
Note leds are polarity sensitive so make sure they are connected correctly.
There is lots of info on the Internet,
Some model boat shops sites have the info you require.
Get back to me if you need more assistance