1. Click on the "burger menu" in the upper right corner > Options > Account settings
2. In the menu click on your Google Apps account name and find the part called "Signature text"
Leave the window with opened Thunderbird and open a new browser window.
3. In this new windows go to https://www.signaturesatori.com/app/user
Fill or update information for your signature.
(Your administrator sets what information you can edit)
5. Save the file to your PC
6. Go back to the opened Thunderbird settings, click in the checkbox "Attach the signature from a file instead" and click Choose
7. Select the downloaded HTML file from your computer and click on Open
8. The patch will be inserted and then click on OK
Your signature is ready.