Open MSI Afterburner. Find the GPU stats graph (temp, voltages, etc etc) and hit Ctrl+F to open the frequency-voltage curve.
The process is the same as CPU or GPU overclocking, you're looking for the lowest stable voltage at a given frequency. A quick stability test it to run something like FurMark, F@H, 3DMark, etc etc. At first you'll test stability for 5 minutes before moving voltage down again. Once you get close to your final setting(s), you'll want to test a bit longer (say 30 minutes).
Google around for "RTX2060 voltage" or "RTX2060 Undervolt" to get an idea of where to start and/or what to expect you can reach.
PS, this question is pretty closely related to
your other thread, probably best to stick to a single thread.