This is the "completion" achievement, where you'll need to get first place in all career events, including promo events, but not vehicle challenges. It is advised that you progress through the entire WSR until you complete it, and then revisit any events that you skipped along the way. Make sure to get first place in all the events, and if you are struggling, make sure to remember that you can change the difficulty to very easy if necessary.
Note: There is a small problem when completing promo events using the timeline. After completing them, they will not be marked with a green checkmark symbol, but they WILL count towards the achievement. Just make sure you get first place in all of the promo events, and you will unlock the achievement.