Once a user account is created it can be used to transfer the files using the SFTP and SCP. The credential of user remain as defined for the UI. In addition, a user can add as many as public keys as needed for the password less authentication.
scp ./2020-03-05_00-02-06.png email@example.com:Home/
sftp -oIdentityFile=~/.ssh/id_rsa firstname.lastname@example.org <<EOF mkdir Home/today put ./2020-03-05_00-02-06.png Home/today put ./2020-03-05_15-28-13.png Home/today EOF