I have not Meta descrption Box

I am using the latest version 3.0.4 but also I haven’t Meta Descrition Box how you can see in this screen shot; please give me a solution.

Thanks

https://www.dropbox.com/s/b8o16houlyylyku/Schermata%20del%202015-11-27%2021%3A15%3A23.png?dl=0

https://www.ads-software.com/plugins/wordpress-seo/