how to add a video from youtube

Hello!
Administrators, please tell me how to add a video from youtube to a post?

Thanks!

 

I'm not an administrator but i tried this:

Hovering the "youtube" purple button on the right of the for to write the post i see the following tooltip:

For this url

i used:

Code:

[youtube]cEwem_8Apvc[/youtube]

and this is the result:
[youtube]cEwem_8Apvc[/youtube]