Start firefox and install the Movable Firefox Button.
You have to restart firefox to make the Addon active.
Right click between the address bar and search bar and uncheck Menu Bar.
Repeat the same but then choose Customize... Grab the Firefox Menu button and move it to the far right side.
Grab the ( with Customize... ) Home and Bookmark button and move them to the left right next to the address bar. Remove the search bar...( drop it in the Customize Toolbar window ).
Now install the elementary theme.
To get the elementary menu icon, you must remove or disable the Movable Firefox Button extension. ( Firefox menu button > Addons )
Next go to the about:config page ( just type it in the URL-bar ) and search for tabs :
Look for the setting browser.tabs.onTop which default setting is true. Just double click it, it will be set on false. We're done....