Bandsintown automatically scans your music from Apple Music/iTunes/Spotify when you sign-up for the first time. If you do not give access then and you want to connect later you can do so in Settings.
On iOS:
1. Tap the Manage page (person icon) at the bottom right
2. Tap on the Settings button (gear icon) at the top right
3. Scroll to Facebook/Twitter/Spotify/YouTube/Soundcloud/playmusic/Last.fm/Deezer
4. Tap Connect or Scan
On Android:
- Tap the Manage page (person icon) at the bottom right
- Tap on the Settings button (gear icon) at the top right
- Scroll to Facebook/Twitter/Spotify/YouTube/Soundcloud/playmusic/Last.fm
- Tap Connect
Please note syncing from Deezer to Android is unavailable at this time.