The PhotoVia App includes the ability to open the photos you've synced to the PhotoVia App into other compatible apps.
To do this, navigate in the PhotoVia App to the photo you'd like to open in another app, and then select the photo so it is in loupe view.
Next, select the "Open-in" button (shown below).
After this, a dialogue will pop up that shows you the apps you've installed that support "Open-in." Simply select the app you'd like to open this photo in.
Whether or not a specific app supports "Open-in" is completely dependent on the specific app itself. If your favorite app does not appear in the "Open-in" dialogue, you might consider reaching out to them and asking them to support "Open-in."