Make sure that the commands are executed as root
Copy raspiBackup.service and raspiBackup.timer to /etc/systemd/systemd/system/
Check the rights and adjust them if necessary
chown root:root /etc/systemd/systemd/system/raspiBackup.service /etc/systemd/systemd/system/raspiBackup.timer
chmod 644 /etc/systemd/systemd/system/raspiBackup.service /etc/systemd/systemd/system/raspiBackup.timer
If the installation path is different, it must be corrected in the raspiBackup.service.
The execution start is defined in raspiBackup.timer. Currently the backup is started every Sunday at 05.00 o'clock (as in the manual). For further customization options see here
If you changes the files, execute: systemctl daemon-reload
Check if raspiBackup is executed with the service unit
systemctl start raspiBackup.service
if successful
systemctl start raspiBackup.timer
systemctl enable raspiBackup.timer
Delete /etc/cron.d/raspiBackup or remove any entry in /etc/crontab to start raspiBackup to disable any other automatic start of raspiBackup. Keep in mind you cannot change the backup time any more with the raspiBackup installer.