Unfortunately the technique to post videos using the "html" tags only works for an administrator for what appears to be a security related concern so I have installed a forum modification that makes posting a Youtube and similar video much simpler.
If you get the ordinary URL (web address) from to address bar of a Youtube or similar web page and past it in it should look like this.
https://www.youtube.com/watch?v=6_xkHuJEPU4