Read here, you will get how to:
1. Playback preview video file;
2. Edit video file, set start and end time;
3. Capture a video scene to be source list item thumbnail image and DVD Menu item thumbnail image;

To edit the an item in the video list, please select it then click button. You will get a window popup as the following .

How to set start spot and end spot of video clip?

Drag the start range slider to set the video start time;
Drag the end range slider to set the video end time;

:Play video file.
:Pause play video file.
:Set current playblack slider spot to be start time.
:Set current playblack slider spot to be end time.
: Reset start time and end time to be original.
: Capture image to be DVD Menu item thumbnail image and source list item thumbnail image.