Teams are able to use the coach feature in league/event matches.
When the match is NOT live:
The player competing as a coach must type .coach (before typing .ready) in the game server. The coach must be on the roster and if necessary pay any League fees or Premium in order to connect to the server.
When the game is live:
In the event that you are not moved to the coach slot (for example when the server needs to be restored or you have forgotten to enter it) simply pause the match and have the coach rejoin the server. Upon reentering the server they need to select the side their team is on (Terrorist or Counter Terrorist) and the system will automatically move them. DO NOT select "spectator" when rejoining the match. Do not type ".coach", ".coach ct" or any other variation, do not try to enter coach commands in CS:GO's console, simply select the side that you are on (CT or T).