In order to crop a video,
- Hover over the orange 'action' button in the center of the video timeline, then click 'Trim Video' from the options
- Move the green marker to adjust the start time of the video. Drag the red marker to adjust the end time of the video
- If you would like to remove any middle portion of the video, click "Add Internal Crop Segment". Use the green and red markers that appear to select the segment you would like removed from the video.