MailChimp
First of all Login into your mailchimp account(If you have no mailchimp account then create on from here).
- Mailchimp Api Key:
After Login go to Account menu from top right side.
Then Go to Extras->API Keys.
Now under Your Api Keys click create a key you will get your api key there.
Copy the key and paste it in the mailchimp api key section in the plugin settings panel
- Mailchimp ListId: Create a list in your mailchimp account then you will get a list id use that id in this field. If you have an existing List then you can get the ID from the settings->List Name and Defaults. there in the right side you will get your list id.