1. In the main menu, tap a document to view details.
2. Click "share"->select a sharing method in the pop-up window (share link/PDF/word/JPG/long image, etc.) and you will find the app as an option.

Note: When you select a doc and tap share, the doc link sharing part will be displayed on the top with the 3rd-party app icons. When you tap the 3rd-party app icon, a doc link will be generated and shared. 

If you don't want to share a doc link, you can tap "Share PDF/JPG" at the bottom instead to share the PDF/JPG file directly.