The next tab is the "Destination" tab. In this screen, in order to back up to your HDA, you must select "Use a remote directory (SSH or FTP). You will want to enter the following information.
ssh://linuxusernamename:password@amahiserveripaddressamahi_ipaddress/var/hda/files/backups/computername
This includes:
linuxusername name - This is your user name for Linux, not Samba.
password - This is your Linux password, not your Samba password.
amahiserveripaddress amahi_ipaddress - This is the IP address for your Amahi server, i.e. 192.168.1.10
/computername - This is to allow you to specify which computer's backup this is.