Instructions
Put up good numbers during the game by draining lots of shots, getting assists and blocking. The better your in-game performance, the more likely you are to be noticed by the league and have your league-wide popularity increase. If you're not putting up numbers, it's unlikely you'll be noticed.
Win awards. This is related to step 1, as the more numbers you put up, the more likely you are to win awards. Each award you win increases your league-wide popularity.
Answer post-game questions with the "Arrogant" option. While this may hurt your team chemistry and your local fan support, it will almost always increase your league-wide popularity.