how do you add an led to a homemade guitar effects pedal?

[Dan Otheram]

I'm building a guitar pedal from a schematic online, but the schematic doesn't include an led on it. To add one on, would I just have to get a 3pdt switch instead of a 2pdt and hook it up on the third portion of the switch? If so how do I hook up to the battery then? Or am I completely wrong about that part? Any help is appreciated.