The key was to set the "Spindle PWM -> analog ch." to "1"
This is located by pressing the "Settings" button, then selecting "I/O SETUP 1" (left upper corner of screen) and the field is on the right...
This probably is all that is needed but it did not work at first because (being a complete Newbie with UCCNC), I think early in my "experiments", I had set the pin/port 1 to another function...
after Clearing that mis-assignment, I think that is when the 10v output started to work.
The last thing was to set up a relay for the spindle which I connected to pin 17 of the AXBB and mapped it to the spindle "M3 relay pin" field ; Spindle screen; top right: pin#17, port #1...
Notes:
1. this field should NOT be called "Spindle PWM -> analog ch." as it has nothing to do with PWM (in my mind)
2. the comment <<You have to setup the PWM spindle mode (PWM min/max. and spindle speed min/max. etc) >> was confusing as right now, I see NO fields relevant to this; these are VFD parameters
3. it would be a good idea (IMO), for the software to insure only one mapping is entered per pin when the "Apply settings" is pressed...
After calibrating, I will probably attempt to build a simple screen-set as I would probably not use most of the buttons on the default screen...