OSX Arduino 3rd party Libraries installation path

Third party libraries usually distributed in zip files.
Old Arduino IDE required users to mkdir a 'libraries' within the app, and then into it manually expand  the zipped libraries... Those days are gone.

With latest Arduino IDE, no unzip at all.
Launch IDE, click menu 'sketch>include library>add .ZIP library...', now navigate to the zip file, say,  ~/Download/IRremote.zip, selected.
done.
yes, that's it.

Already expanded to ~/Document/Arduino/libraries/IRremote.

Restart IDE for that libraries' example code.

For more detail, see the link in readme.txt inside the libraries folder.