Before start with this guide, there is everything you will need:
Connect AutomatorWP with Mailchimp
1 – In your Mailchimp dashboard, click on your avatar at left-bottom > Profile.

2 – Navigate to Extras > API keys.

3 – Click the Create A Key button.

4 – Copy the new API key to place it in your site.

5 – Come back to your site, navigate to AutomatorWP > Settings > Mailchimp, paste your API key and enter your Server Prefix in the fields.
Note: To find the server prefix, go to your Mailchimp account and look at the URL in your browser. You’ll see something like https://usXX.admin.mailchimp.com/, the usXX part is the server prefix.

6 – Click on Save Credentials button to finish!
That’s all! Now that you have successfully connected AutomatorWP and Mailchimp, you are able to automatically manage your Mailchimp contact, tags, audiences, and campaigns based on your site activity like purchases, e-learning and community activities or any of the triggers supported by AutomatorWP.
In addition, you can check the automations samples page where you can see some samples of the possibilities of this add-on.