First you will need to visit the Mozilla website to download the latest version of Thunderbird here: https://www.mozilla.org/thunderbird/
This will download the file for example: thunderbird-45.5.1.tar.bz2 then we need to move the file into the /usr/ directory:
# sudo mv ~/Downloads/thunderbird-45.5.1.tar.bz2 /usr/
# cd /usr/
# sudo tar xvf thunderbird-45.5.1.tar.bz2
Once this has completed extracting you will then need to press the key in between ctrl & alt, which is usually the Windows key.
Then in the search box type main menu and press enter. Then in the main menu click on “Internet” which is on the left side bar and then click “New item” on the right side bar.
Now on the top left side there is an empty icon button press on that and navigate to:
Computer > usr > thunderbird > chrome > icons > default and select the “default256.png”
In the name section type “Thunderbird” and for the command section type “/usr/thunderbird/thunderbird-bin” and then click on “Ok”
Now that Thunderbird is installed and you have created a launcher you can press the Windows key and search for Thunderbird or even add it to your favourites.