A motor shield is for motors. a servo shield is for servos. They are not the same. If the servos are a fairly small size you can control one or two of them for testing directly from the arduino pins. Check out the servo examples in the playground or in the IDE and most of them tell you where to connect everything to get a servo to sweep or whatever function the example is for.
What shield do you have? You just said motor.. some shield allow multiple things depending on how you set them up. http://www.adafruit.com/products/81