The procedure is: Loosen the four silver cap screws. Adjust the four black cap screws for chain tension and plate alignment. Tighten the four silver cap screws. Done.
It took me a couple reads and some staring at the pics to understand this. In this application, I believe the four black screws would be referred to as "jacking bolts". You are making quite a splash by posting one great idea after another!
Whether someone is interested in high-performance or better efficiency (same miles from a smaller battery pack, or, more miles from the same pack) giving the motor 2 or more gears is one of the best options. Keeping the motor in its efficient RPM range during more of your trip, means less heat in both the motor and also the controller (less heat-damage, and also less battery watts used as waste-heat). Motor-gears also means less peak amp-draw from the battery, which translates into good performance from average C-rate packs.
I have recently determined to use a Nexus-3 that is driven by a small motor (for all of the reasons stated above), and I have studied gearing a motor at length.
Matt has shown that for early adopters, a high-quality system with premium components will sell for a price that allows you to survive in a competitive hobby. BB-drives have the potential to provide both great hill-climbing and also higher speeds, where most builds must choose only one or the other.
This is a VERY good development!