If you're using control via an external controller, likely it'll be best to ditch the pot as it could interfere with the settings (if not set it to mid position where it'll have least effect) . Normally you'd connect the 0...10V output to where the wiper connection of the pot connects and ground to the anti-clockwise connection: unless there's a separate input for external control. What driver board is being used for the spindle?? I've investigated a little bit about such things as I'm in the process of converting my pillar drill to a similar DC motor.