While reporting bugs- there is option to upload video. If you were not able to do it- when validator will mark your bug as pending than you can edit and add video. Even if you are not able to do it- than place your video in google drive/dropbox and share the link in the comment section of the bug.
Now a days You can also make a video by any tools(e.g.: Fast stone capture) and upload to you-tube and put your you-tube video link in comment of report, if there is no option to add video in your report.