Backbench account - Sign Up, the personal account will always remain free to use.
Mailchimp account- sign up, create a list and add recipient into the list, create your Campaign and customize your content of email also add the list to your campaign.
Backend
Select +, in the upper right corner to create a Module. For example, say "mailchimp.js" and select CREATE or hit Enter.
Copy and paste the code module from below.
Replace USER NAME, PASSWORD and API key from mailchimp setting section (create a new api key using create button).