OK. Made a little progress!
Configure > Control > Output Signals (tab)
Enabled #10 & 11, Device PoKeys_42701 PE, Output Names Relay 1 & 2.
Now need to figure out how to trigger #10...
Would be nice to map it to the Spindle CW / Stop (M03 - M05) button functionality, then I could add M3 and M5 commands in my G Code.