how to find a short in a circuit, learn me

So along with what appears to be a turbo that enjoys burning oil...

im having a problem getting my SCT X4 to tune my car. after a couple of days of hunting down the issue it seems like the device is shutting down from being shorted out from my wideband O2 sensor. I could go into detail on how we determined this if it helps; long story short is that it works w/o the AFR gauge plugged in and vice versa.

he said something about finding proper resistance, grounds and other things... i had no idea on what he was going on about so since y'all seem like a smart bunch i figured my best bet was to come here for an ELI5. my only tool for this is a cheap multimeter, what can i do?

think of a simple circuit. Power (+ battery) > wire > switch > wire > device > wire > ground (- battery). A short means that power connects to ground while skipping the device.

Unplug the device, and start at the + side of the device connection and work toward the + battery. Check for continuity (low resistance) between the + side of the device and ground. Continuity confirms your short before the device. Next move to the - side of the switch. Check again. When you no longer find continuity, you know the short is in the wire in between where you are and where you last checked. Keep moving inward until you find the short.