Go to left sidebar section Settings then Email. On this page you will be able to edit the email address and email from name for the emails that get sent out and you can also build, change, or edit your email signature.
Whatever is saved on this page is what shows up in the email templates.
FYI that when you are viewing email templates, we will show this in the email templates - [email signature]
This is a shortcode and where you see this, your saved email from the email settings page is what will be displayed on the email that is sent out.