Olympic Games: London 2012

You will need 2 controllers for this. From Main Menu, select Party Play and then down to Challenges, you will see there are 8 challenges. In each challenge there will be 3 events in which you must perform to a certain standard. Once you have taken part in each event you will be awarded stars based on your performance. You must score set amount of stars throughout the 3 events to successfully complete a challenge. Do this for all 8 challenges and the trophy will be yours.
Note: Some of the targets are quite high so this can be difficult.