If you've played any of the other years installments of NHL, it's exactly the same every time.
When you are a defender and between your goalie and the attacking opponent who has the puck, try and deflect an incoming shot by holding
and moving the
either left or right to get your stick in the way of the shot. If you block the shot with the your stick you should get the achievement.
I personally found it easiest to do on Threes Circuits and Rookie setting.