Although there may be other ways of posting Youtube clips here, this is the way I do it. Although many members already know how to, this is for those who don't.

To embed a Youtube clip, in the Youtube clip screen, click on the address shown in your browser bar at the top of the screen. That's the bit where it starts with http ://youtube .com". The address should now be highlighted.  Then press Ctrl C to copy the address.

Come back to here and then in the Post Reply Box, click on the 4th icon from the right, the one which looks like a couple of film frames. In the File/URL box press Ctrl V to past the address in the box.

I then tab from that box to the next box, and in a couple of seconds the clip picture appears. You can play about with the dimensions but I generally leave that line blank. Then click the Insert button. You come back to the Post Reply screen and you will see an empty box where the clip will be shown. You do not see the clip appear on this screen.

When you click the Submit Reply box, you will see the film appear in your posted reply.