Open iTunes and click on Films from the menu on the left.
iTunes open on Films pane
RECOMMENDED: Open iTunes Preferences (Under Edit menu on Windows, or iTunes menu on Mac), click Advanced tab and ensure Copy files to iTunes media folder when adding to library is ticked.
If iTunes doesn't copy the files, it will use your Desktop version! Not good.
Grab the new file from the Desktop (the one you made in Handbrake) and drag it into iTunes, releasing it on the main window. If this is difficult, another way is to open the iTunes File menu, select Add to Library…, locate the file and press Choose.
If you can't drag it in, find your file manually.
Navigate to your file.
The file will now copy into iTunes (check the green window at the top). When complete, it will appear in the main window. This may take a few moments.
Copying the file into iTunes.
Once the film has copied into iTunes, you can delete the version on your Desktop.
Note the new film has appeared.
