In Newzik (App or web), it is not possible to import files directly from a GDrive directory shared by another user.

This is because only the contents of your personal drive ("My Drive") are visible in the import files navigation view.

However, you can get around this limitation by creating a shortcut on a shared drive and adding it to your personal drive.

To do this you just have to:

1. Open Google Drive in your web browser
2. Select the "Shared with me" section in the panel on the left 
3. Select the shared drive you wish to access 
4. Tap on the option menu (vertical "...") and select "Organize"
5. Tap on "Add a shortcut" option 
6. Select a location in your personal drive

You can now access the contents of your shared drive via this shortcut.