If you have some other guys and girls who also have Arma, and who are obviously your most elite soldiers, they can be part of the training session as demonstrators.
At my university we use Blackboard Collaborate. So basically you would need teaching software that the students can see the instructors screen (there are multiple options for this, I hear a lot of talk about Zoom for instance). If not everyone is able to play Arma I would k̶i̶c̶k̶ ̶t̶h̶e̶m̶ ̶o̶u̶t̶ ̶o̶f̶ ̶t̶h̶e̶ ̶p̶r̶o̶g̶r̶a̶m̶m̶e̶ setup some kind of interactive viewing session where an instructor can show for instance some manoeuvres on the map and using first person perspective, based on a mission that he created. At the same time, get acquainted with the editor, there are lots of tutorials on youtube and elsewhere. I would say: play some of the general gameplay tutorials to get on how the game works.
