You definitely do NOT want to just connect pins from your COM port to the micro motor controller. There is a simple circuit in the instructions for making the necessary inverter/level converter that requires just a transistor and a couple of resistors.
I misread the original post and was thinking of our micro motor controller. The micro servo controller has the circuit built-in, so you just need to connect the serial output from the computer (pin 3 on a DB9 serial connector) to the RS-232 input on the servo controller (and connect the ground line).
If you just want that circuit, take a look at the micro motor controller instructions.