Growing up I have never used these types of bobbers, with the spring on the bottom shaft, and I have some in an old tackle box and need to put it on my son's rod with nightcrawler. How do you rig one of these up?

Pull the spring down, insert your line into the notch, and let the spring return to it's original position which will lock the bobber onto the line. If you want to adjust the depth you are fishing, you can simply loosen the spring on the bobber and slide it up or down to your liking.