input 24V

output 12V split to 2 rail with on/off switch.

*1st thing, make sure you step down your input voltage.
you can make a simple voltage regulator (7812 vreg will be usefull), to regulate 24V to 12V, or just simply do a 1/2 splitter to get 12V from 24V.
but bear in mind there will be heat as energy transformation there.

2nd, since you wanna have LED there, you need resistor to protect your LED. try 1kohm .

so you are done.

rgds,
albert