You'll want to make a file that will always be in sync with the unit, so that you don't have to retrieve the data every time you run the program. Of course, you don't have to do it this way, but that's how I do it, so that's what I'm going to recommend.
Click on the disk button at the top of the main window and click Save As... to save the file. This will be your scratch file.
Now click the disk button again and click Save Copy As.... Save it under a different name. This will be your backup in case something valuable gets overwritten in the snapshot.
To restore a backup use the Load Copy menu item to load the backup into the snapshot, then use the Transmit Snapshot Data button to transmit to the TX81Z.