Setting MailChimp API:

Go to Dashboard >> MailChimp For WP >> MailChimp >> Setting your API Key then clickSave Changes“. To learn how to get API key, you can refer document of MailChimp.

mailchimp

Create MailChimp Form:

Go to Dashboard >> MailChimp For WP >> MailChimp >> Forms:

mailchimp-form

Demo Mag WP theme has a style MailChimp form available, just copy and paste below content into your MailChimp form:

<h3>Sign up to our newsletter!</h3>
<input type=”email” name=”EMAIL” placeholder=”Enter your email” required>
<button type=”submit”><i class=”fa fa-paper-plane” aria-hidden=”true”></i></button>