To create an e-mail signature in the new Yahoo mail please follow these steps:
- Go to http://mail.yahoo.com and login to your email account
- Click Options near the top right of your mail account and select Mail Options
- Click Signature on the far left side navigation of the mail options page.
- Select the option for Show a signature on all outgoing messages and type in your signature.
- When you navigate away from the page click OK to save your signature