I follow the steps but I get the djay application to open with …
The following example shows how to use this feature with the Dropbox app, but any other app supporting “Open In” with audio files will work as well.
Load a song from Dropbox:
Mark the song as “Favorite” by tapping the star icon.
Tap the “Share” icon in the bottom left corner.
Tap the “Open in…” icon.
Select djay. The song will automatically be loaded to the currently inactive turntable.