Short of the instruction manual lying on the counter next to the control panel, how would anyone know how? When I've been assigned as an ECO in the playoffs, all I do is show up and mash the remote switch on or off. The "civilian" handles everything else. Its the easiest $70 in football
Correctly operating the game clock should be a relatively smooth process, provided;
* The "Civilian" running the scoreboard knows what he's doing, or,
* The view is unobstructed by fans standing on seats directly in front of you, with or without umbrellas, or,
* A small booth with "pressbox coaches" from one, or sometimes both teams, asking stupid questions or making "questionable" comments about every call that doesn't go their way, or
* An announcer, 5 feet away, who thinks ESPN is secretly auditioning him, or,
* Stadium lights that are too old, too low or just too weak, or,
* Game officials along either sideline that are far harder to pick up in front of the team area (I understand white knickers are gone forever, but with all the benefits of our black trousers, the fact is they make game officials a lot harder to find on the field. That could be improved, considerably, by migrating NFHS shirts to the wider white stripes used at the NCAA level), or
* Game officials who sometimes forget to give clear, difinitive signals repeated enough so that someone who may for good reason be focused elsewhere, might see and pick up the signal, or
* Umpires and Referees who sometimes forget to consistently pick up and repeat signals given by wing officials in front of the team areas, who may be obstructed, or lost, behind (or in front of) 40, or more players & coaches, cheerleaders, band personnel and photographers and other "special people" allowed on sidelines. or
* A Referee who is willing to advise an exciteable coach that a TO begins when the official HE told he wants one acknowledges he heard it and signals, rather than when he decided he might want a TO and then goes to find his wing official to tell about it.
When things go as expected, with no major surprises or problems, operating the game clock can be a very enjoyable, and rewarding, experience.