The flat running events involve simple joystick waggling, which must be balanced with accurately-timed button presses to clear the hurdles - hitting them or breaking stride causes a loss of momentum and thus time. For jumping and throwing events, you must build momentum by waggling and then press the button to throw or jump at what you feel is the appropriate moment.
For each event, points are earned based on how well you do (this can be based on your running time, or how far you throw the javelin or discus, etc...), and the player with the most points at the end of the decathlon wins the gold medal.