To elaborate: I'm sure that they had familiarized themselves with this piece of equipment during training, but before the bulk of them joined the military would they have had a rough idea of what a parachute was/how one was used?
Yes, they would. Parachutes had been in use a hundred years. One of the "daring aerialist" feats at fairgrounds in the 1800s was for one of the men that went up in a balloon to leap out and parachute down. They were used by the men in observation balloons in WWI. They had appeared in lots of movies, and in the 1930s (Popular Science Monthly) the first "flying squirrel" gliding suit for parachutists appeared.