Head here, you'll need to install Bolt like normal using the Green download button. You can import the entire zip on your 2.2.1 installation. Then on the left side, click the download bolt v2 button. This is a child style that you can import directly under the Bolt (PARENT DO NOT EDIT). You can edit/rename the v2. When you go to upgrade you'll only upgrade the main Bolt Parent.
Let me know if that all works. We're going through a site revamp with new docs/store that'll make this clearer.
The easiest method will be to download the Bolt dark CHILD style from the same link above, import as a child of your style. That will it will inherit most of your changes (footer settings, logo, other items). From there you can set up the light bulb: https://pixelexit.com/documentation/light-switch/