Aaero

To earn this achievement, you need to complete the DLC song Outsiders on normal difficulty.

To select the song, choose normal difficulty from the menu and scroll to the bottom. Here you'll see the DLC songs listed. Choose Outsiders and play through the level. Once you complete the level, the achievement will unlock.

Below is a video of my playthrough that I made if you're struggling. I got 5 stars on this, but you don't need that. Simply complete the level and you'll get the achievement.