FROM YOUR PHONE
You can use a different WIDGET (snap or snapper serial) and the SAME REFERENCE to upload new pictures to an existing file. Please be aware that the file needs to be OPEN for you to add new photos to it!
To understand more about widgets and how to make them available on your device, please check this article.
FROM YOUR PC
1. From your PC, you can upload images, but also other items such as a PDF. To do so, open the file you would like to update, click on the '...' button on the right upper corner and hit "Upload" from the drop-down menu:
2. Click "Drop files here" (or literally drag and drop files in there from your system).
3. Include an optional comment and indicate if the images are ok for sharing
4. And click "Upload".
That's it!