Sometimes the Finder may not change the icon(s) right away. To see them immediately, close, deselect, and reopen the folder containing them.
All commands operate by selecting icons, then choosing a command from the DD menu.
You can also combine files or folders into a single file, or split large files into smaller pieces.
DiskDoubler makes files smaller using a process called compression. By compressing files, you can make more space on your disks, or shorten the time it may take to send a file over a device such as a modem.