The shield plugs in directly into any shield-compatible Arduino such as Duemilanove, Diecimila, UNO, Leonardo, Mega R3+, ADK R3+. The only pins required to run are the Ground, 5V and SDA + SCL I2C control pins.
For backwards compatibility with old Ardunos, SCL is connected to A5 and SDA is connected to A4. UNOs already have this connection on board. If you are using a Leonardo or Mega and want to use the A4/A5 pins, cut the traces on the top of the board between A4 and A5 and the two pins next to them labeled SCL/SDA.
If you are using a Mega or ADK R2 or earlier, you will have to solder a wire from SCL to D21 and SDA to D20
Since I2C is a 'shared bus' you can still connect other I2C devices to the SDA/SCL pins as long as they do not have a conflicting address. The default address for the shield is address 0x40
This shield has two power supplies. One is VCC - that is the 5V power from the Arduino, it is used to power the PWM chip and determines the I2C logic level and the PWM signal logic level. When this power supply is working you will see a red LED. The red LED must be lit for the Arduino & shield to work! Plug in the Arduino to USB or a wall adapter to provide it.
To power servos you will need to also connect the V+ power supply - this is the power supply for the servos. (If you are lighting up single LEDs you may not need this power supply.) This power supply should be 5 or 6VDC. You can connect this power through the blue terminal block. There is reverse-polarity protection in case you hook up power backwards.
Nearly all servos are designed to run on about 5 or 6v. Keep in mind that a lot of servos moving at the same time (particularly large powerful ones) will need a lot of current. Even micro servos will draw several hundred mA when moving. Some High-torque servos will draw more than 1A each under load.
Good power choices are: