CFO

Can anyone tell me how to use CFO in multiplayer. The simulation rate is greyed out. I have seen other players using this facility ut I can't work out how it works.Can anyone help me ???
Flight Simulator and other chat
https://forums.simviation.com/phpBB3/
https://forums.simviation.com/phpBB3/viewtopic.php?f=4&t=17625