Very simple, just beat all 15 opponents in the Western Conference Circuit in NHL Threes Mode.
To easily get 3 stars play on rookie and set the goal limit to 4, just shut out the opponents and you will get 3 stars.
Collect all 45 stars to also obtain the Star Collector achievement simultaneously.
Tip: You may need to go back to the select circuit menu and select the Western Conference Circuit even after obtaining the 45 stars to get the achievement to unlock.
Happy Hunting Hockey Fans!