Have you looked at the user's guide? It gives an example of what to send in MiniSSCII mode: "For example, sending the command sequence [255,18,254] will move servo 2 all the way to one extreme of its range in 180-degree mode." I wouldn't recommend starting out with this example though, because it is not a good idea to command your servos to go to the extremes of their ranges. How about you try sending 0xFF 0x00 0xBE while in MiniSSCII mode? Do you know how to send hex bytes via CoolTerm? Judging by the screenshot of this page, it is possible. I don't have a Mac to test it on though. If you have access to a PC computer somewhere, you can use the Pololu Serial Transmitter on it.