Signatures are listed under their relevant group. When selecting an email signature, you will get a few options on what you can do with the signature as well as the preview of the signature showing on the right of the screen.
The “Display Name” is only used as an identifier for the signature and not for the actual “Name” field in the signature. For example, you could have the “Display Name” set to “GB”, and the “Name” field of the signature to “Gordan Banjac”. Most of the time though, you would have the same Display Name and Name fields.
The “Email” field is used as an identifier and is also the email address who will receive the signature when you click on the “Email to…” button.