There are four ways to load a clip into the trimmer:
Enter a valid filename in the file entry widget.
Click the open button next to the file entry to use the file dialog to browse for a file.
The pulldown menu on the file entry lists all the existing clips in the project. Choose a clip from the pulldown menu.
Drag a file from your file manager (e.g. Nautilus or Konquerer) to the Kino window.