1) Find a YouTube video.
2) Copy the address link of the YT video at the top of your browser by highlighting it and holding [CTRL] & pressing [C].
3) Click on the 'film icon' above the text box.
4) Click your pointer in the drop down box.
5) Paste the link into the drop down box by holding [CTRL] and pressing [V].
5) Press the [ENTER] key.
6) Click [Insert Video]
7) Click [POST] to post your video and/or text.
*Note: You can use the right mouse button on PC to accomplish the same thing as the CTRL buttons.
This may seem complicated when reading but it works similar to vBulletin.