Here is the link to the photo moments app help guide for visitors: https://www.zenfolio.com/us/z/help/support-center#/customer/en/portal/articles/1934800-photo-moments---for-clients
This one is the general downloading help guide for downloading for visitors: https://www.zenfolio.com/us/z/help/support-center#/customer/en/portal/articles/408308-downloading-photos-from-zenfolio-to-your-computer---for-visitors