No: it should “just work.”
PhotoStructure may need to be granted read access to your Photos library (via macOS’s permissions-by-app system). macOS is supposed to pop up a dialog saying “are you OK with PhotoStructure reading your Photos?”, but in practice, rendering this dialog is unfortunately hit-or-miss.
These settings can be checked (on Mojave, at least) via System Preferences > Security & Privacy > Privacy, and adding PhotoStructure to either the “Photos” or “Full Disk Access” sections.
(In general, it’s a good security practice to only give an app the minimal permissions it needs to do work, so just giving access to Photos should be sufficient for PhotoStructure)