After Selecting it fill there required details, there will be 7 fields that you need to fill, One is Protocol that you already have selected as SFTP.
Location Name: It is used to identify your location as you can add Multiple SFTP backup locations.
Server Host: Its the location of your SFTP for eg sftp.mywebsite.com.
Port: The SFTP port usually the default port is 22.
SFTP Username: Username of your SFTP account.
SFTP Password: Password of your SFTP account.
Backup Location: It's the name of the folder where your files will be saved and it requires an absolute path.