Click the youtube button... it's up there with the B and i and Quote etc. You'll get a simple youtube bbccode. In between the codes, you copy/paste the YouTube id. You know, that funny part at the end of the URL.
The ID is the bit at the end there, after the "=".
Feel free to ask if you have trouble doing this. I'm hoping to figure out how to allow it to just let you paste in the entire YouTube link in between the tags... apparently there might be a bug with that now. But it works with the ID, so ... yeah. Good times. Happy embedding.


