First,Click on the small "YOUTUBE" red icon above when posting something in your sYc reply box.
Next,copy and paste the last part of your youtube link after it's = symbol,in between the two youtube brackets.
Example:if it's entire link is
https://www.youtube.com/watch?v=KATEnhTYGfE,only copy & paste KATEnhTYGfE.
Then hit "Preview post" to make sure it appears correctly for you.
If so,hit submit. Voila!