This the best video on how but long.
This is short and to the point.
Basically get earth from the board and even the power in earth is good. Positive side of the voltmeter to the center of the trimpot on the stepper and see what you have.
99% of the steppers I buy have the trip set very high. There is maths to work out the numbers but I would start about 0.4 - 0.6v run a test print and feel the motors. They should be a little warm but not hot, feel the steppers they should be warm but not to hot to touch.
If you have cooling on your motherboard that will help a lot.
Thing to know if you have miss matched steppers and motors. Motors can run hot and most are rated as high as 80degC and still run fine but steppers don't like too much heat. So if you can run the numbers on the stepper that seems good you can run the motors hotter and get away with it.