Using this Arduino motor shield with a pi may be problematical, first off it looks to run at 5v were as the pi GPIO works on 3.3v so you would need to interface the 3.3v to the 5v to prevent damage to the pi and possibly make the shield respond to signals.
Secondly this shield is design to work with just 3 control pins on the arduino by using a 74HC595 shift register so you would have to make your pi software work with this as well, yet anther level of complexity were you would need to fully understand the operation of the motor shield.
There are other L293D motor driver boards out there that are designed for the pi and would be easier to use.
Examples specifically designed for the pi
https://thepihut.com/collections/roboti ... s/motozero
https://thepihut.com/collections/roboti ... 1059504792
Example general L238 motor boards that will work with a pi
http://www.ebay.co.uk/itm/Dual-L298N-H- ... SwceNZV4is