To enable ssh on a Raspberry Pi if you do not have access to a keyboard and monitor, just run the command:
touch /Volumes/boot/ssh
The catch is that you need to have access to the micro SD card and have it connected to your computer. Then open up terminal and type the command above. touch is a utility command that updates the timestamp of an existing file or creates a file if it does not exist. On a brand new install, this ssh (no extension needed) will not exist so it gets created.
Next, put the SD card back into the Raspberry Pi and boot it up. ssh in with the following command:
ssh pi@raspberrypi.local
You can also use the local IP address as well if you know it.