DC Motor Pinning the Ada Fruit Moto Shield with the Mega2560 R3
Well because an Arduino Mega2560 is pretty much and UNO with a longer rear end, try seeing the UNO in the MEGA if that makes any sense. Then just put the shield in like a normal shield that you would put on a UNO. Most UNO shields are compatible with MEGAs. Then you just use your shield like if it was on an UNO.