Mine have screw terminals, so no soldering. I have a few of each of these, they seem interchangeable:
https://www.amazon.com/gp/product/B00MIJL4OChttps://www.amazon.com/gp/product/B019SYX7BM(and many others, some with V and A displays built in, which will be in my next order)
1) Attach your source, set the output V with the Voltage screw
2) Unscrew the Current screw all the way (it'll tick tick tick but won't actually stop)
3) Connect your vmeter in series with the lamp
4) Check the LED spec sheet for amps
5) Increase the Current screw until flicker stops and you get solid light output, note the amp draw and double check the LED spec sheet
(I actually gave an extra half turn of the CC screw to avoid starving the LED)
If you think you may have bumped or moved one of the screws, check it all again. Better safe than smoky.