With Smartware you can’t - it’s back-up software not sync software. The whole point of back-ups is that if you lose/delete/corrupt the local copy then the back-up one will be there as a safety net and not auto-deleted too.
If you want such folder/file synchronisation instead of backing up, then you will need to use a different software solution to achieve that. But if you want to continue using Smartware, the only option for file deletion is to do it manually.
