FORZATHON Live events will start at the beginning of every hour. They will appear on the map as a pink circle ten minutes before it starts, you will get a pop-up notification on the screen five minutes before it starts. Drive to the circle and wait within the circle. The event will begin when the hour starts. Then complete all three rounds to finish the event. Do this twice more in consecutive hours. (EXAMPLE doing the 9:00, 10:00, and 11:00 events) to complete the achievement.
I did read that you can come off the game after you complete one event and then go back in the game before the next event starts but that never worked for me so I had to stay on the game and do three in a row to get the achievement.