Video thumbnails should be automatically be created, however you might wish to change the thumbnail to a different image. Follow these steps to change or upload a thumbnail that best fits the video you uploaded:
1. Log into your Admin page. Select "New Videos" under Add Media.
2. Once you're in the Videos section, select the video with the incorrect thumbnail.
3. Upload your own "Video Thumbnail" use the dimensions 356x200 jpeg
4. Once you have uploaded or updated the thumbnail click "Submit"