start PI ZERO

https://www.raspberrypi.org/help/quick-start-guide/

1) download the raspBian Jessie
https://www.raspberrypi.org/downloads/raspbian/

2)Installing Raspian with a Mac
"Apple Pi Baker(http://www.tweaking4all.com/hardware/raspberry-pi/macosx-apple-pi-baker/)" provides a similar feature set as Win32 Disk Imager. Once your card is inserted and recognised, select it from the list on the left; then select your downloaded .IMG file from the right, and click Restore Backup.