Voltage is set by the motor wiring, typically inside a box on the motor if it's a big motor, or by removing a sheet metal plate on the back if its a smaller motor. The side of the motor, near the data plate that tells you manufacturer, HP, usually has the wiring diagram. If not, it should be inside the cover where the wiring is done. Attached is an example of a wiring diagram from an old GE motor. Do not follow this for your motor, but look for similar. Also note if the motor is reversible that get the right direction CW/CCW. Determine what direction its running currently and set it the same way. Usually involves swapping a lead if necessary.