Open your Thunderbird software. Click on “Tools”. This will open a list of options.

Scroll down the list and click on “Account Settings.” This will open a dialogue box that displays the default identity. If this is not the email account you wish to work with, scroll through the list on the left-hand side to locate it. Click on the appropriate email account.

In the identity display, there is a check box with an “Attach this signature” with location box and “Choose” button below it.

Use the “Choose” button to locate your signature file. Once you locate the file, select it, and click “OK”.

Verify that the correct file and location has been input into the address bar. If it has not, search and select again. Once the correct file and location is in the location bar, click “OK” on the identity display.

Use the “Write” option to open up a new email. Your signature should be displayed on it. It will not display as an attachment, but as part of the text.

Verify that your signature shows up as desired by sending yourself an email to another account. If there are problems with the display, you may need to alter the signature file itself in order to correct it.