Hello Luis Miguel,
It's been a while, but this is from my notes:
create ssh key with command ssh-keygen in bash
Then in clish:
add ssh hba hostname <ip address of server> public-key access-mode standalone file /home/admin/.ssh/id_rsa.pub
connect with ssh to server with -i and answer yes... the server's fingerprint will be added to the known_hosts file.
To test one time: backup scp ip <ip address of server> path <path to backup on server>/ username <username> password 1234
Then I simply created the scheduled backup in the GUI...