Just go through the procedure. Load a sacrificial film into a Paterson Super System 4 tank (because they're very common used and don't cost much to buy new) in daylight to show how it works, then show a light-proof bag, explain that when doing it with a real film you need to load in darkness, then produce one you've already loaded.

Next video can cover chemicals, temperatures and mixing the correct quantities, then pouring them into the tank in turn while timing with a clock or watch and emptying afterwards. Finish with removing the rinsed negatives from the tank, squeegeeing, and attaching film clips before hanging it somewhere relatively dust-free to dry.

Now a split - one about scanning, one about printing traditionally. Cover the kit first, then the actual process. Maybe use night vision gear to show the darkroom in action, unless IR light bothers B&W paper?