EDIT: Just gave it a test run. Copy the entire URL of your youtube video (eg for above: https://www.youtube.com/watch?v=8X1aaFyNBMg).. for reference I only used to use the code after the equals sign on the old forum. Use the WHOLE link now. 

type the code:
[ youtube ]PASTE YOUR URL HERE[ / youtube ]

^ but don't have spaces in the square brackets.

Should work. Let me know.