The prisoners started to arrive at the canteen at the same time as Olaf got there with the weapons and ammunition.
They gathered in the center of the canteen. It was a lot of inmates, but that place was made to accommodate multiple people at the same time, so it wasn't a problem.
Everyone picked up their segregated part of the guns. The ones who knew how to assemble the weapons helped as they could to raise the productivity of the work and save more time.
Olaf was told to lead them to do so. Casper was clear when he said that organization would be everything in that plan.
If the prisoners forgot that they were a team, not a bunch of strangers fighting individually, they would fail miserably.
It was hard on Olaf to bear such a responsibility, however Alfar would be there too, and Vick was the only acquaintanced of Casper that knew how to deal with people better than the Dark elf.