rodgoslin wrote:What one can learn, intuitively from four shaded rectangles, I've no idea. There seems no indication of what the options entail, or will produce.
Those four "rectangles" represent the different themes. Click on one, then click apply - the whole desktop will be refreshed then.
If you cannot switch those and don't understand the documentation, you may want to search for some youtube video that shows how to do this.
5 seconds search yields: https://www.youtube.com/watch?v=uApBtxcpZlU
Here's one that explains how to install new themes: https://www.youtube.com/watch?v=RxwFcfNRink
Honestly, cannot understand what's so hard about this.