To make a screen recording, click on File menu and select New Screen Recording in QuickTime.
Using the Open dialog box that comes up, navigate to the location of your file, select it and press the Open button. You can also go to the File menu and select Open File. Alternatively, you may drag the file into an already open QuickTime window. Since QuickTime is the default media application for Macs, it will automatically open.
If you desire to carry out limited editing on an already existing media file on your computer or removable media in QuickTime X, simply double-click the file in the Finder.
