You can view/open files in Android via the mobile app.
To access your files from your Android device:
1. Open the Sync app
2. Tap on the three horizontal lines located at the top left
3. Select either 'Files' or 'Vault' to view their contents
4. You can select the 3-dot menu beside a file
5. Select 'Open with' and then you will be prompted to choose a program to open the file with (if you have the third-party app installed)