Carlsen starts his defence today of the World title, against Challenger Sergey Karjakin.
The 12-game match in New York City starts at 18.00 GMT this evening. The official site is here. It costs $15 to watch the games and listen to the commentary, but there will almost certainly be other portals where the live action can be followed, such as Chess24.com.
If the score is even after 12 rounds, there will be four tie-break games, with a possible 'Armageddon' fifth game if the scores are still level. The full rules and playing schedule can be viewed here.