1) From the Projects screen, tap the Project you wish to share to go to it's Summary screen.
2) Tap "Share Report" to generate and preview your report.
3) Tap the icon in the near top right of the screen to show the Export Options available.
4) Tap on Theme and select which one you wish to use from the list shown.
5) Tap "Options" to make further changes or "Regenerate" to save this theme change immediately and update your Report.