Hit button to add video files from your computer;
Hitor to change the order of source files.
Hit to remove the selected item from source list.
Hit to edit video clip start time and end time.
Select the video file to be edit, and click "Edit" button on the right side.
Then you will get the edit dialog as the following picture show.
: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.