I'm not sure exactly what you mean. Do you mean like this?
If that's what you mean, you can use the media button on the RTE, or use the [media=youtube]thestringoflettersandnumbersintheurl[/media] code if you have the RTE turned off.
Here's a screenshot of the text editor. I'm on mobile, so I can't mark the specific button you should use, but it should be the third from the right on the top row.
If you mean actually uploading a video as a file to Iwaku, I have never tried it, so I honestly have no clue.
Also, I moved your thread to the Help Desk because I think it belongs here rather than the Media Shops and Requests forum, but it can be moved back if needed.
Political intrigue, fantasy, futuristic, sci fi lite, superheroes, historical fiction, alternate universes. Smittings of romance, but only as side plot.