Your signature appears automatically at the bottom of all messages you send.
SelectComposein the left sidebar, then selectUse Signatureunder Signature.
If you decide to disable your signature in the future, go back to this screen and chooseNo signature.

punch in your desired signature in the text field.
Use the options in the toolbar to adjust the font, embed links, and format the text.
SelectSave Settingsand shut the Mail prefs window.

Remember to stash your changes.
What Is an Email Signature?
AOL Mail Signature Tips
Email signatures can include all sorts of information.

Focus on what’s most important so as not to overwhelm the recipient.