To add a carb to your beer can, as in to open the tab and 'pop' a hole in my back. It allows the beer to flow smoother. Basically the same technique as shotgunning, but you only add a tiny hole on the top back of your beer so you don't have to drink it all at once, but instead at leisure.
The term 'Kennedy' refers to the late President, whom was shot in the back of the head, presumabley by Lee Harvey Oswald.
"I got a fresh beer"
"I have my swiss army knife, want me to Kennedy it?"