So what exactly do you need to know about them? The "small" ones are probably 3mm ones. There's also a little larger ones that are 5mm and then 8mm and 10mm but those are big ones.
Basically the longest of the 2 legs is the positive(+) and the shorter one is the negative(-).
You can hook them up to any 5V or 12V source, but 5V would be the easiest because it's closer to the actual voltage of the LED so you can use a smaller resistor. YOU MUST USE A RESISTOR
So if you're using 2 UV LED's, wire them in parallel and hook them to a 5V source. Parallel wiring is when you connect all the possitive legs together and connect it to the power source and then connect all the negative legs together and connect it to the grounding source. A series wiring is like what most people think of when you just connect all the LED's in a row end to end.
So for 2 UV LED's, you're gonna wanna get a 47 ohm 1/4 watt resistor as well if you do parallel wiring and you can put the resistor anywhere between the power source and the first positive leg of the LED.
Hope this helps and let me know if you need anything else!