This feature is only for registered users, then must be logged in. Tu cut a video and generate a download button use the scissors icon from below the video player:
Vídeo duration must be greater than 1 second and less than 20 seconds.
Crop, Pad and Add slow motion options will show when available depending on your video aspect ratio.
Select "Add Stories" to post a comment to Stories section. Video and comment will be displayed up to 48 hours.
Then the Download buttons should then be unlocked and ready to use.