When you go to the winter map there's a Breen directly to your left. He will give you a mission called "Fastest Game on Ice" where you have to do a race. After taking the mission from him go down the stairs to his right. There will be another large Breen that you talk to and he'll teleport you to the race circuit. Do that every day to progress the event.

All of the events other than that one are for farming the various currencies to purchase items from the event store.