Get your MailChimp API Key and choose your List ID

First, login to your MailChimp account. Then, click on your avatar on the bottom left corner of your screen and click Account.
Click on Extras > API keys:

Click on Create A Key if you have no key, then copy your API key:

Go to your WordPress dashboard and click on Zeus Elementor, then click the Integrations tab and paste your API Key in the MailChimp block:

Now, add the MailChimp widget of any page or post you want and select your List ID: