How exactly do i change themes on firefox?

I would like to use the mario theme and i already have the newest version of firefox but i have no clue how to change my firefox to the mario theme i have downloaded the mario theme and i choose USE THEME and it says restart firefox to use the theme but it duznt work what should i do?How exactly do i change themes on firefox?
go to the top toolbar of Firefox. Click:

Tools%26gt;AddOns%26gt;Themes



There is a link on the bottom right corner of that menu that says ';Get Themes';How exactly do i change themes on firefox?
Answer the questions below. If you have not tried any of these tips try them and see if they work.



have you completely close all firefox windows?



have you double checked that you have the mario theme selected?



Have you tried to restart your computer and then open firefox (do NOT just log off user; you must restart or shut down).
you open mozilla firefox then tools tab addons click on themes tab if you you want to install themes in your bowser. if you already installed it then you click you use theme then you close mozilla firefox and you open again.