All they're saying is to stick the bolt in from the engine side, and put a nut on it, tightened down to the firewall. Then attach the MSD to the bolt and attach with another nut. The first nut keeps the bolt tight and located so you won't have to have an extra set of hands holding the bolt to get the nut started. You'll probably still need someone when it comes time to tighten.
It's a great idea...and even more usable the reverse direction for more commonly replaced items like fan relays, so you don't have to get your wife to go under the dashboard to hold your nuts.
That last part didn't sound quite right.
