About setting of button to send to email address and setting of automatic sending to email address

The first question is how to edit the form for sending a password to an email address when you forget your password. Specifically, when I created a form to send a password to an email address, I don’t know how to set the send button to send to the email address that I entered. The second question is how to automatically notify the registered e-mail address to that effect, for example, when the account registration is completed or when a reply is received in chat etc. Is to say.