how do i change voltage of my cpu

Check in your BIOS the voltage settings, change the CPU Voltage option from "Auto" to "Manual" and select the voltage that you want.

Be aware, use stock cooler or higher voltage can damage your CPU, motherboard or both. Tom's Hardware or me we aren´t responsible if that happen.

I suggest you let us know the cooler that you have and depending of the temps, don´t go above 1.5V on air since that is a limit for AMD CPUs.