Hi,
Thanks for contacting us.
Firstly, we cannot get access to your website although we entered /wp-login or wp-admin, it didn't work.
Please check, then give us your information again so we can help you to check the second question.
For the first question: We also support to enable a sign-up checkbox. Please see the attached image 1
To have it, please install MailChimp for WordPress plugin then go to Customizer > Site Enhancement > then Enable MailChimp Subscribe then enter MailChimp API key.
You can check it, then feedback us soon.
Best Regards,
NooTheme