DSM 6 only: Installation of packages published by any publisher must be allowed before Safe Backup Plus can be installed. This setting can be enabled from the Package Center; in Settings > General > Trust Level, select the "Any publisher" radio button and accept the settings.Installation of Safe Backup Plus on a Synology NAS follows the same process as installing any other SPK:
.spk file downloaded from Safe Backup Plus Server
DSM 7 only: Permission issues will stop the backups from working correctly. Please follow this guide here https://help.safedatastorage.co.uk/portal/en/kb/articles/dsm-7-permissions to get the backups working.