Use the Offset Mode, and do a -0.05V negative offset on the Vcore. You could go lower after that, but that's just to start.
First though, use the Auto voltage, run something like Cinebench R20, and note down your temperature, Vcore voltage and CB score. Then undervolt, and check those again. You don't want your performance score to drop (at least not too much), but you'll want to see those thermals go down.
okay heard that Ill try that later considering I dont want to spend another hour testing everything again.