It's quite easy, just select the "youtube" option in the purple tabs at the top of the new post window, or use standard BBCode formatting: [youtube]VIDEO URL GOES HERE[/youtube]
The important thing to remember is that you'll just be copying the URL from your browser's URL bar, not using the actual embed code that youtube provides.
For example, to embed the below video, I used this code:
Code: Select all
[youtube]http://www.youtube.com/watch?v=q56PID1kzeE[/youtube]