Ok,
Wiring diagram - readable please!
And CODE please (inline with </> code tags)
You do realise that motor shield uses I2C to communicate, so you don't use PWM on the Arduino.
Maybe worth checking the Adafruit example code.
Also check what voltage the motors require (probably 5-6V), which will need to be fed into your shield.
(Preferably not from the Arduino +5V as noted above)