Where to wire fake led

I want to add a fake led on the drivers side of my dash since I don't have an alarm and can't get one now. If I get the kind with the 3 wires, Ignition Positive, Constant Positive, Ground, where should I hook them. I have a 89 Buick Century Limited. Would it mess up my radio if I share those wires with it? If not where would be another place to get these wires, I'm new to this so I don't want mess up anything. I know under the steering wheel is a good source, but it really looks confusing looking at all those wires. What would I need to hook the constant-positive straight to the battery?

Thanks for the reply, but just to be sure, the ignition harness is in the bundle or wires under the steering wheel, near the floor? Also, I see my starter wire is there too, would it be possible to make a starter disable switch using that wire? What other wires would be needed.

 

Sorry for all the newbie questions, but I'm new to this and really don't want to mess anything up since I have to drive the car to work everyday.

Thanks for all the help guys, this is really a great site.

 

One more question, after looking at the diagram, I think I need a four prong/pole switch. I understand all the wires except the 2 "To Srarter Output Wire", are they used only if I have an alarm, or are those the ones I need to use for the switch, if so what is the block with all the numbers, the ignition?