To backup SQLBackupAndFTP, according to the selected schedule, you have to specify User Name and Password. If you use Windows Authentication, please specify your User Name and Password you use to log in Windows OS. Or apply your SQL Server credentials if you use SQL Server Authentication.
It seems you use SQLBackupAndFTP version 10 or older which are very old versions and no longer supported. Please install the latest version SQLBackupAndFTP version 11 and check if it works smoothly https://sqlbackupandftp.com/download