Anyone know how to DEL a mail account?

I couldn't figure out how to alter my email signature, so I stupidly tried to alter my email account by creating it again, then delete the old one.  But can't find ANY way to delete an existing mail account, only add new ones.  Any help would be greatly appreciated.

Also, I still would like to know how you EDIT mail account settings, such as signature.  Thnx.