To remove pictures from the Private Gallery, open the app, tap on TOOLS tab and select the Vault feature.
Enter your pattern (or numerical password).
Tap on the icon with a checkbox to select the photos you want to remove.
Select the photos you want to remove and tap on "REMOVE FROM PRIVATE GALLERY".
A confirmation message will show up. If you really want to move back the selected photos to your Android's gallery or SD card, select "Yes".