for example, if you wanted to post the video showing the time trials in the square (already posted obviously but I am using it as an example)
The video URL (web address) is
In this case (they are all different) the bit you need is BxIr_waHeHc
all you do is copy and paste that into a thread the same way you would for any other txt or link, and then highlight it with your mouse or keyboard and then click the "youtube" button in the menu above your text.
when you submit the post the forum will then insert the video