Ask-Tell-Dismiss is a standard tool used by referees to manage players, coaches, sideline parents and fans. Be calm and professional. Apply the least amount of pressure needed to control the game. If an action so warrants, you may immediately go to Tell or Dismiss.

Ask-Tell-Dismiss for players

(1) Ask and/or warn the player to stop unacceptable behavior.
(2) Tell the player to stop and issue a caution (yellow card).
(3) Send off the player (red card).

Ask-Tell-Dismiss for coaches

(1) Ask the coach to stop unsporting or irresponsible behavior (for example, dissent).
(2) Tell the coach to stop and that you are now formally giving a caution.
(3) Dismiss (aka, send off) the coach from the game if their bad behavior still persists. The game may continue if there is a registered assistant coach or other registered team official present. If not, terminate the game.

Ask-Tell-Dismiss for team supporters

In addition to being responsible for players, the coach is responsible for the behavior of team officials, parents and fans (supporters).

(1) Ask the coach to speak with an unruly or dissenting supporter to calm that person down. Wait until the coach successfully does this.
(2) If the bad behavior persists, tell the coach again that they must deal with the offender right away and that the game will not continue until the offender leaves the area. Tell the coach you are issuing them (the coach) a caution.
(3) If the coach cannot handle the situation and remove the supporter, then dismiss (aka, send off) the coach. Do not continue the game until both the coach and the offending supporter leave the area. The game may continue if there is a registered assistant coach or other registered team official present. If not, terminate the game.

Do not actually show a yellow or red card to a coach. But do say verbally that you are cautioning them or dismissing them.