Hello,
I am wondering if it would be useful to add "platform specific" FAQ's to the "Installation & Trouble Shooting"
Topic?
I am brand new to Arduino and right out of the gate I encountered a problem that in the end, turned out to be a software version/hardware computability issue.
One of the things that tripped me up was trying to locate my "Arduino15" folder. Given how automated the installation process is on a MAC (my platform), no amount of searching was turning up that folder. It took me hours and hours of searching to discover that current MAC OS hides the Library folders and even makes them non-searchable - to protect you from yourself. 
While a lot of folks tried to help me through that, none of them were MAC users so they didn't know this. Frankly, I don't think I have had to interface with any of my Library folders in the last decade so I didn't realize this.
All of this being said - On a MAC, to find your Arduino15 Library you do the following
hit Command+Shift+G from the Mac desktop (or Finder > Go > Go to Folder) and type in
~/Library
to temporarily access the Library directory in the Finder.
When you are done, close this window and it will no longer be visible.
This took a big investment of my time to sort through and I'd love to have it posted in an FAQ here somewhere for future MAC users.
Thanks.