Sign-up to MailChimp by entering your email, username and password, and click the activation link in the email you subsequently receive. You then have to fill out some more details that include your address.
Click on Lists in the MailChimp top navigation bar and then Create List.
Go to your WordPress administration area and click “Plugins”. And then click “Add New” to find the MailChimp Widget plugin for WordPress. Install and activate.
Enter API Key. Activate widget. Easy!