Creating the backup can be as easy as adding a new cron job in the above screen you showed, to run at 2:55am (example) with something like:
(uncompressed)
mysqldump --opt --default-character-set=utf8mb4 -u'ADMINACCT' -p'PASSWORD' xenforo > /var/www/html/MYDOMAIN/mysql_backups/xenforo-backup-$(date +\%F).sql
(compressed)
mysqldump --opt --default-character-set=utf8mb4 -u'ADMINACCT' -p'PASSWORD' xenforo | gzip -c > /var/www/html/MYDOMAIN/mysql_backups/xenforo-backup-$(date +\%F).sql.gz
ADMINACCT = your admin login account name
PASSWORD = your admin password
MYDOMAIN = domain where database operates
or a fancier example for backup with short day of the week for 7 day rotation:
/bin/mysqldump --opt --default-character-set=utf8mb4 -u"MYSERVERUSERNAME-HERE" -p"MYSERVERPW-HERE" DATABASE_NAME > /home/ACCTNAME/back/xf-bkup-$(date +\%a).sql
This last one will store 7 backups on your server, named by the day of the week, so make sure you have room. You can put them in a folder not reachable from your website. (EX: BACK) If you want it off site, there are several ways. Some send it off to s3, some download it to a local linux server at home, some use an old windows program like FTPSYNCH go ftp in and grab it a few minutes after the cron runs daily.
You could also have it run a second cron to make a TAR file of the site contents, with something like:
tar -cf /home/ACCTNAME/back/xf_files.tar /home/ACCTNAME/public_html/
I hope this is useful, to get you started.