Dotann.
You put the URL in the title, not in the post. That was the first mistake. To post properly follow this...
Go to the video you want to post.
Copy the entire URL.
Come to the post, look at the top of the post where you see the options to change font, size, etc... You will see a 'film strip' icon. It's the one second to last.
Click that icon and post the URL into the box that pops up.
Click OK.
Now the video should show when you put up the post.
Just a side note, some Youtube URL's have an 'S' in the http.. like this 'http
s://...' If you see the 'S' after the 'http' after you paste the URL, take the 'S' out, otherwise the video will not post. If there is no 'S', then there is nothing you need to do to change it. Just past and post.