A Tutorial courtesy of threefiveandeight:
Edited By Way updated the process and added pics
How to post a video from youtube:
Find the video you want to share on youtube.
Highlight the last part of the url. everything after the = (7Rt_1JSWKuY)
Copy it(ctrl+c) then paste it (ctrl+p) into the forum text editing box.
Now you hit the full editor box under the text field.
Highlight the text by either drag clicking across the text or pressing ctrl+a
Left click on the "youtube" button located above the text editing box.
Then it will look like this you can also from the normal text box just add the youtube code brackets [youtube][/youtube]
If you're then finished with your post, left click on the "submit" button under the text editing box. All done! Yay!
Here it is in Action