Ubuntu: How to add thunderbird in messaging menu

In ubuntu how to add the thunderbird in messaging menu in top panel under mail indicator.

1.Please confirm the following file if thunderbird already installed.

sudo gedit /usr/share/applications/thunderbird.desktop

2.In terminal open the  empty text file under name 'thunderbird'

sudo gedit /usr/share/indicators/messages/applications/thunderbird

and add the following line in the abovesaid file and save.

/usr/share/applications/thunderbird.desktop

Now right click on mail indicator in top panel the 'Mozilla Thunderbird Mail/News' menu appeared.