protein shakes before or after a workout?

Ok so I just got a CRAP LOAD of Muscle milks light, chocolate flavor. My goal of training is to get leaner/ cut. I am a heavyweight but my limbs are rather thin. I have nearly no bulky muscle but I can lift ALOT. Should I chug down a muscle milk before or after a workout?

I do alot of cardio/pylometrics. If I happen to be banned before I can think you I will still come to to thread to read.
Thanks in advance!