Obtain your MailChimp API Key
Login to your MailChimp account and click on the Account/API Keys and Info Link to obtain your API Key.
Obtain your unique list ID
Under your list settings click on the the "List settings and unique ID" link to obtain your unique ID.
Why isn't the email address being added when testing?
Your list may be set to use confirmation opt in. This feature requires that the subscriber manually confirm the subscription before they have been added.