I am well aware that this is not an APPLE product, however this IS an Apple SUPPORT group, so I see no problem asking other users if they know the answer.
While I have sent the developer an email through the app, I don't expect much help based on his web page for the app. He already has on the page:
2. Importing photos into the app
On the photo list screen, sort by long tap, select and save to email or Camera roll.
Note, the heading says Importing, but the actual step doesn't say anything about how to do that, just how to sort the pictures already imported. He's Japanese, and his support web site is all in Japanese, so I don't think he understands English very well. Still hopeful, though, that either he or a HELPFUL user on this site can provide assistance.