You can do that in Appearance > Install Plugins.
- Once installed, go to the plugin’s Settings page and enter your API key.
- Add a new Block and look for the Mailchimp for WordPress Form Block.
- Go to MC4WP > Forms to customize the Sign-Up Form.
Example Form Code from the AMAYA demo page:
<h3> Never miss out </h3> <span class="subscribe-text"> Sign up for our Newsletter and get the latest Coffe Bean news, unique offers and access to exclusive products. </span> <span class="subscribe-form"> <input type="email" name="EMAIL" placeholder="Enter Email" required /> <input type="submit" value="Sign up" /> </span>