Hi Benny!
One of the features of our WordPress backup plugin is the ability to manage scheduled backups using a web server’s crontab system, and it looks like DirectAdmin comes with that functionality so you should be able to configure a Backup Schedule in the Total Upkeep settings that will handle that for you.
The configuring a backup schedule will automatically create a corresponding cronjob on your web server that triggers the backup at the specified time and will ensure that all of the proper authentication is associated with that job.
Please let us know if you have any other questions for us Benny!