I thought I understood Sketch->Include Library->Manage Libraries but I on a clean install with only one sketch, I tried to install "SdFat - Adafruit Fork" as opposed to Tools->Manage Libraries
I was trying to install the Adafruit Fork version for just my sketch as I have other sketches that use SdFat (non-Adafruit Fork).
I find that "SdFat-Adafruit Fork" library does not appear in a Library sub-directory of my sketch but rather in the $HOME/Arduino/libraries directory
Help with my misunderstanding would be appreciated greatly.