The GUI for managing the files is opened by going to ControlPanel and clicking, under "Maintenance", "Backup/Restore". To stop some files or directories from being backed up, click the tab that says, "Excluded from Backup (.xfiletool.lst)", then at the bottom, right hand corner of the window, there is a drop down menu that has the items "File" and "Directory". You can choose whichever one you want to exclude, then click the button "Add" that is to the left of the drop down menu. it will open up a popup window titled "Select <file or directory> to be added to /opt/.xfiletool.lst". Use the file manager in that window to choose the file or directory you want to exclude from the backup.