How do I power and work this led screen?
Lol,
I'm afraid it's going to take a bit more than just that..
We'd need a clear picture of the bottom, or if you can check to see which chip drives the LCD (if any)...
The bottom is just silver and then the pins coming out the side. No chip or anything.
Looks more like and LCD than an LED to me, but it is kinda blurry.
So any history? Clairvoyant component identification is not a well practiced art form.
In short it looks like one of several tens of LCD displays.
Try rubbing it with a soft cloth, do you see outlines of seven segment characters? That could narrow it down.
However, I suspect it is a raw LCD display and will need a driver so it's not going to be easy to interface to.
Ok, so it is a LCD display. Good thing I only paid 75cents for it.
Lumex Numeric Display ?
I think the light changed in here because I can faintly see outlines of numbers and then a V, the ohms sign, and an A. So I'm guessing it's from an old school multimeter.
The pins are the same design as those Lumex displays. So I'm guessing one of the pins is a ground and the others control which part is illuminated?
and the others control which part is illuminated?
No LCD displays do not light up. They in effect block the light, that's why they are dark. It is not just a matter of feeding a voltage to the segment you want to highlight you have to apply several rather complex waveforms who's phase changes according to what you want to illuminate. that is why it is best using a display driver chip.
For an overview see:- Liquid-crystal display - Wikipedia
Or for a driver look up the data sheet for a HCF4055
No LCD displays do not light up. .... according to what you want to illuminate
Hah! Gotcha! [smiley=laugh.gif]
GONG (as they used to say on the yes / no interlude)
I got it right on the first sentence then slipped up on the second.
You win the coconut 
However, I could say you illuminate what you don't want to show but that would be cheating as I didn't think of it at the time.