From the Super Mario Wiki
Hockey is a Court & Field Sports Event that appears exclusively in the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The objective of the event is to score more points than the opponents. The starting best record for this event is 9pt(s).
In this event, the player selects a team of two Tricksters, and competes against a team of the other two Tricksters, a pair of Koopa Troopas and a pair of Chao. The player must use the circle pad to move their pair of characters along the two green lines at the sides of the hockey court so that they can reach the ball once it gets close enough to them. The characters pass between each other automatically, and will continue to do so until one of the characters misses the ball or they score a goal. The characters must travel along the hockey pitch until the reach the "D" shape around the goal, and once a character receives the ball in this area, they will attempt to score a goal past the Shy Guy goalie. Occasionally, the goalie will return the ball, but if the player is able to reach the ball before it goes offscreen, they can take another shot at the goal. Once a goal is scored, some extra time will be added, starting with five seconds, and then decreasing by half a second with each goal until it reaches three, which it will constantly remain at. As more points are scored, Shy Guys will start appearing between the two characters and will return the ball to the same character who hit it if it is aimed towards them, indicated by the Shy Guys displaying and orange flash. That character must then hit the ball instead of the one on the opposite side. If either character misses the ball, they have attempt that goal from the start, however no more Shy Gys will be added and the player does not receive a time penalty. As more points are scored, more defending Shy Guys are added. The event ends when the timer, which starts at 30 seconds, runs out, and the amount of goals scored prior to that point will be the player's total.
Move: Move the Circle Pad up/down.