halfapage

Cool now strangers can track them without effort.

I declare bankruptcy!

Using the multimeter you can find out the polarity of each LED. You could use ohmmeter, continuity, or diode mode for that. There are lots of tutorials about how to do that, you can use those keywords to look around. Your meter might not have all those modes available, you have to check and use one of them.

A bit of advice about LED in displays like those: either some of them or even all of them might have one "side" of polarity tied together. Like, all cathodes or anodes might be internally connected together just for the sake of reducing the count of terminals, and therefore traces on the board. Look out for this if something doesn't make sense while you look for individual diodes.

Do you have an idea for providing, say, 5VDC?

Do you have soldering flux and some way to wipe the tip if it gunks up?

Hmm.. For starters, I would recommend you do something a little bit more basic with it for the sake of increasing you knowledge from "close zero". Don't connect mains voltage to it even if it has a connector for that etc..

Playing with the display would be pretty fun. Each section that lights up is a separate LED, so you can imagine that you could light them all up all by yourself if you figure out how they are connected.

You could start with learning about LED polarity, and how to power them without risk of them burning out. After you figure this out, you could then research how microcontrollers (preferably for starters on Arduino format and the like) could let you control them.

I wouldn't recommend trying to use this boards functionality, like taking power from it and such, for now. You could return to that later, armed with more knowledge.

If you do not feel confident with your soldering skills enough to desolder the display, you could cut traces leading to it's terminals to effectively cut it out of the circuit. Those traces look like they would be easy to repair if you wanted to, but for now you could just solder wires to display on board and play with LEDs alone.

What equipment do you have on hand? Any DC power supplies? Multimeter? What kind of soldering iron?

For the chip part, it all really depends. Starting from scratch with one already embedded in an unknown board design with no documentation might be a herculean task even for experienced tinkerers. I would recommend starting small, it really goes a long way.