On Windows, you can find an uninstaller next to the program in the Start Menu. However, if you can't, all you need to do is:
Head to Start Menu > Control Panel
Click on "Uninstall a Program" under the "Programs" section.
From there, find the Duplicate Files Finder and click on it. You should see an "Uninstall" button show up at the top of the pane. Click on that, and it'll open up that program's uninstaller. Hit next, and when it finishes, the program will be completely removed from your system.