for the 360 version if you pull up the game on the my xbox tab, I think its my xbox, the tab with the picture of the game that you can click to run the game, if you pan to the right you should be able to find a full list of all DLC content available for the game and simply click on it to download assuming you have the points for it.

If not then go into Xbox Live Marketplace and do a search for the game, it will pull up with all the DLC available that way.