An API key helps you integrate your MailChimp account to your website and other services. If you download a plugin for MailChimp on your WordPress website, you may be asked for an API key.
To create your API key you need to sign in to your MailChimp account and click on Account.
Then go to Extras > API Keys.
Scroll down the page until you find Your API Keys, this should be empty – simply click Create a Key.
Now your API key has been created and will always be in this location.