Hey Clive,
you may read the fine manual at MASSO Documentation: VFD Spindle Examples, and also read your VFD’s manual for the connection and the settings.
What you need to use a VFD on the Masso Elite, is control of spinde speed over an analog 0–10 V voltage wire and control of spindle FWD/REV/STOP over a wire to a programmable input terminal of the VFD. These settings are usually called “Source of Speed command” and “Source of RUN command”.
Unfortunately, the MASSO G3 does not support controlling VFDs over a Modbus Serial communications interface.
The relay output at the right side of your VFD diagram is for switching the spindle coolant pump on and off.
See also
Onefinity Elite Series Installation and Operation Instructions (PDF) , page 38