WordPress.org

Where can I see the Double Opt Contact Form ?

Can be found on every User's Profile including Admins. You could create a demo user to see it lively from a User profile.

Who will receive the sent emails ?

Automatically and Always, all emails goes to the indexed-as-number #1, current Blog Admin Email.

Whom will I reply to hem/her ?

Reply-To address is already set up by Double Opt Contact Form for your convenience. Just choose to reply to the email message.