Superstar Challenges are a great way to expand your roster and unlock new Superstars.
By completing the objectives associated with a Superstar Challenge, you can earn enough Superstar Shards to recruit that Superstar.
To view available challenges:
Go to the Home screen.
Tap SUPERSTAR CHALLENGE.
Select a Superstar to view their objectives and rewards.
After recruiting a Superstar, be sure to revisit their Challenge page. You can continue completing objectives to earn additional shards and increase their Star Rank.