To SHH into your BeagleBone from OS X go to http://beagleboard.org/getting-started#step2 and download the drivers. I recommend to use the links on that web site, when I first did this I used the links provided by the on-board web site of the BeagleBone. That led to old drivers and thus SSH did not really work…
Anyway, after installing the drivers and rebooting your mac you can SSH into the BeagleBone. If there was already a connection any time before you will need to add the new SHA fingerprint to /Users/user/.ssh/known_hosts (where “user” is your user name). Simply open finder, tap CMD+SHIFT+G, paste /Users/user/.ssh/ and open the known_hosts file in an editor. Find the ip address of the BeagleBone (192.168.7.2) and add the new SHA fingerprint right behind it (separated by space). The fingerprint will be provided by the SSH command when it fails due to changed remote identification, so just copy it from there.