How do I make FTP the source? How do I backup files from an FTP server?
When creating a new profile simply select the option to Backup from an FTP server at the appropriate time during profile creation wizard.
If you already have a profile
SyncBack V7: modify it, select Easy from the Click For Options button (top-left of the window) or select Easy from the list on the left, go to the Type settings page, and select the second option (to copy Destination to Source, the exact text may be different depending on the labels you have given to your locations).
SyncBack V6: modify it, go to the Decisions -> Files settings page, click the "Click here to see more options" box at the top of the window, and click the second button (to copy Destination to Source, the exact text may be different depending on the labels you have given to your locations).