How to download youtube only with fitur Mozilla

We can download video  youtube site without add software example internet download manager, or download with web pages, for example keepvid.com that very occupied and need more time.
The following will download the video is just other way to use features available in mozilla

First you must add your Mozilla add-ons
 

Or you can open in new tab Mozilla

https://addons.mozilla.org/id/firefox/addon/easy-youtube-video-downl-10137/

second you download the add-ons !..

  

And third if your download finish you  must install.

You can chek your install success or No.

Clik tools- choose add-ons (ctrl+shift+a)

If your install success,you will find like this.

You also can check, what is different with your browser ?..  open www.youtube.com

Now  you can download with easy..