ok i have the USB cable and have connected it, i set the board type to UNO and also saw that the USB port appeared so selected it for communication. On the board the user LED flashes so i see this means there is a boot loader installed. When i try to download the "blink" example sketch i get a compiler error for board type. and in the log i see many messages like below. In the start here section it suggests this might be because of an older MAC X version but i have 10.7.5, im sure the PC is communicating with the board as i can retrieve board info like serial number etc.
Arduino: 1.8.1 (Mac OS X), Board: "Arduino/Genuino Uno"
/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/../lib/gcc/avr/4.9.2/../../../../avr/bin/ld: /Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/../libexec/gcc/avr/4.9.2/liblto_plugin.so: error loading plugin: dlopen(/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/../libexec/gcc/avr/4.9.2/liblto_plugin.so, 2): Symbol not found: _environ
Referenced from: /Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/../libexec/gcc/avr/4.9.2/liblto_plugin.so
Expected in: /usr/lib/libSystem.B.dylib
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board Arduino/Genuino Uno.
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.