Use the embed options from where ever you are getting the video from. Use submit to submit the video. If it doesn't post the video, you can always edit your post for the next 30 minutes. If you can't get it to work, leave the link in the post and I am sure one of the mods or admins will be glad to edit the post for you so the video shows.
"Cu è surdu, orbu e taci, campa cent'anni 'mpaci."