You can create an email signature via our RoundCube mail client, all you need to do is to navigate to your cPanel account → Email Accounts section:
Select which email account you wish to manage:
There you will be able to access RoundCube:
Then navigate to Settings -> Identities section and the email signature will be displayed on the bottom:
You can also enable HTML signature and add an additional picture of your choice to your signature:
If you wish your HTML signature or Hyperlinks to be displayed when composing a new email, be sure to change Editor type as HTML:
If you want to know how to create an email signature for hPanel - check this article.