John
Are you doing this with mach3 or linuxcnc ?

You should find the optical spindle encoder sensor wire it’s got four coloured wires in on cable. It went to the LH end of the board that you sent me. Has a flat inline style connector
On my vmc190 then optical sensor on the machine end of this cable was caput but I found a suitable optical sensor in my bits and bobs tin
You will need to establish what sensor is being used and google it for a data sheet
In principle the optical sensor is a led on one side and a sensor on the other they will share a common ground line
Connect the led negative to the Bob ground, the plus side of the led to the required voltage on the Bob (this is where the data sheet comes in handy) let’s assume it’s 12volts
Then the trigger wire to the Bob input pin that you wish to use
Then you rotate the spindle you should see the pin flash one per revolution in mach3 or LinuxCNC
There should be two optical sensors you want the outer one of the two for the single. Pulse per rev (only thing that mach3 will use)
You do the same on the inner sensor and map that pin to the A of the encoder. The single pulse per rev is the Z connector
In linuxcnc you can do all of this with the step config wizard

Paul