When you find a video on Youtube you can't post the normal way, you can cut the title and paste it onto the search bar and find the exact same video with a shorter address and post that code, or you can cut the address between the = and &

The link you posted would work like this ...

https://www.youtube.com/watch?v=x9j6DE6RnSk&feature=emb_title

x9j6DE6RnSk

Just add the [yt] code at either end.