Access the Journey by tapping the top banner on the home screen to open your profile and then tap the Journey tab.
The Journey is meant to give you a more visual way to track your progress and be a new source of rewards.
Gather enough stars by playing songs to rank up in the Journey!
Reaching new ranks adds new songs available to unlock in your collection. This is also how you unlock access to songs of Hard and Extreme difficulty, as well as access to other features in the game like the Tour pass and Events.
What if I have unlocked everything?
If you don't have any more songs in the "available in boxes" section in the collection, simply collect enough stars to get to the next Rank and unlock access to more songs.
When you reach the new Rank, the "available in boxes" section will reappear with a list of the new songs available to collect.